Best Oil for Rover V8s ?
Discussion
What is the general concensus of opinion to the best engine oil for Chimaera / Griffith V8s (500s in particular)
TVR recommend Mobil 1 - many are of the opinion this is too thin.
I have used Mobil 1 Motorsport as advised by one dealer.
Other dealers have advised that Castrol GTX Magnatec 10W 40 (semi-synthetic I think) is best as it 'is more suited to the engine's charateristics'
I have heard stories that lubrication to the rear of the engine (cam area) can be poor due to the inherent low oil pressure. Therefore the best choice of oil seems to be important.
So who is right - all opinions appreciated.
TVR recommend Mobil 1 - many are of the opinion this is too thin.
I have used Mobil 1 Motorsport as advised by one dealer.
Other dealers have advised that Castrol GTX Magnatec 10W 40 (semi-synthetic I think) is best as it 'is more suited to the engine's charateristics'
I have heard stories that lubrication to the rear of the engine (cam area) can be poor due to the inherent low oil pressure. Therefore the best choice of oil seems to be important.
So who is right - all opinions appreciated.
If you're just topping up, use whatever is already in it and don't mix a synthetic (Mobil 1) with mineral/semi-synthetic.
Mobil 1 0w40 is still a 40 when hot, but I'm putting myself up for abuse here. The '0' winter rating indicates it is a bit thin when cold, which is not so good, but also that it has a flatish viscosity~temperature curve , which is probably good.
In the absence of TVR's recommended 5w50 I use the Mobil 1 15w50 anyway, as at least one expert suggests.
When I changed from the 0w40 that was put in at a service I noticed less tappet noise on the up side, but a noticeably slower rate of increase of oil pressure on the downside.
Going to higher viscosity not only saps engine power but reduces flow and hence the heat transfer away from the bearing surfaces.
That's all opinion, just like the myriad of other threads you'll find.
Cheers,
Andy
Mobil 1 0w40 is still a 40 when hot, but I'm putting myself up for abuse here. The '0' winter rating indicates it is a bit thin when cold, which is not so good, but also that it has a flatish viscosity~temperature curve , which is probably good.
In the absence of TVR's recommended 5w50 I use the Mobil 1 15w50 anyway, as at least one expert suggests.
When I changed from the 0w40 that was put in at a service I noticed less tappet noise on the up side, but a noticeably slower rate of increase of oil pressure on the downside.
Going to higher viscosity not only saps engine power but reduces flow and hence the heat transfer away from the bearing surfaces.
That's all opinion, just like the myriad of other threads you'll find.
Cheers,
Andy
Three page essay on the working of the oil police in the bible.
Cam problems were reported in the days of Duchhams 20W50 which knocks that one on the head. Some Mobil 1 cars have had cam problems but so have others using all the best alternatives therefore there are other issues but with most religious dogma, let's forget about this as it doesn't fit.
The oil lube system is radically different from the 50 year old design so that old chestnut is a urban as well.
I use 15W50 Motorsport in the Griff. Kendalls 20W50 in the 520 (but it needs an oil change after every trip out on the track!)
Cam problems were reported in the days of Duchhams 20W50 which knocks that one on the head. Some Mobil 1 cars have had cam problems but so have others using all the best alternatives therefore there are other issues but with most religious dogma, let's forget about this as it doesn't fit.
The oil lube system is radically different from the 50 year old design so that old chestnut is a urban as well.
I use 15W50 Motorsport in the Griff. Kendalls 20W50 in the 520 (but it needs an oil change after every trip out on the track!)
rat said:Haven't you got that back to front
Mobil 1 0w40 is still a 40 when hot, but I'm putting myself up for abuse here. The '0' winter rating indicates it is a bit thin when cold, which is not so good, but also that it has a flatish viscosity~temperature curve , which is probably good.
The oil gets thinner as it gets hotter reducing to 0 (not really 0 but damn thin in Mobil 1's case)
Oil gets thinner as it gets hotterMulti-Weight oils are intended for usage with wider temperature ranges than
single weight oils.
The spec goes like this; for 5W30
The "W" signifies the temperature at which the oil will pour through a
specified diameter hole in a specified time. Or, in other words, is the
stuff a liquid, or is it molasses, or is it tar? Note, to a Chemist,
molasses and tar is a liquid; to an Engineer molasses may or may not be a
liquid (practical folks Engineers are) and tar is not a liquid. So for
5W30, the stuff will pour at 5 degrees F. For 10W30, the stuff will not
pour (to the spec) at 5 degrees F, but it will pour at 10 degrees F. This
spec is to tell you how cold you can get and still (safely) start your
engine.
So, around here in Camelot where it never gets too cold, 10W30 works just
fine. 5W30 or 0W30 isn't necessary. Just stay out of the Sierras in late
January during a cold spell unless you have multi-vis oil.
The "30" is a viscosity, or flow rate spec for "real fluids." So, at normal
oil temps, this tells you the relative thickness of various lubricant
products. Note that the SAE test spec for engine lubricants is not the same
as the one for gear oil, so SAE50 engine oil isn't the same viscosity as
SAE50 gear oil. Usually ... there ARE exceptions (sigh).
Again, note that going up in temperature lowers the viscosity, so (for
example) SAE40 at 230F will have the same viscosity as SAE30 at (say) 215F.
Multi-Vis Dynosour erls use an additive (same stuff STP buys from Chevron)
to create the multi-vis part. These oil molecules are long polymer chains
that roll up into a knot when cold, and unravel , eventually getting almost
rod like when they get hot. Somewhere around 265F, these molecules decide
they've had enough of this rod-shaped stuff and decide to change back into
a knot. What this means, is you take oil with this additive and go up to
Walt Boeninger's Corvette computer limit of 320F, and you've had it; the
stuff flows like alcohol, and you've bought yerself an engine rebuilt. So,
Multi-Vis dinosaur oils should NOT be used at the track if you are one of
those who scoffs at my viewpoint on proper oil temp and blythely runs yer
erl above 250F. The other thing that happens, is these long molecules get
sheared (broken in two) mostly at the lifter cam interface and the stuff
ceases to be multi-vis anymore, and gets runnier at normal engine
temperatures. So, oil DOES wear out in some instances.
Now, to make things complicated, what I said about the multi-vis additive
above, don't apply to synthetic oils. Synthetic oils will tolerate higher
temperature without distress than dinosuar oil. Their viscosity vs. temp.
curve (usually) ususally has a bit slope to it that is different than
dinosaur oil base. The only downside that I know of for synthetics, is they
are somewhat inferior to a good Pennsylvania based oil for extreme pressure
situations, ... like a flat tappet on a cam lobe when you use mongo valve
springs and run astronomic RPMs (above 7,000RPM).
Another interesting thing I have heard from several oil experts (including
the Chief Engineer at Red Line) is that all racing oils "wind up being
SAE20." In other words, thicker oil molecules (which are microscopically
longer) get sheared during operation. And race engine speeds shear lots
faster than freeway speeds. So ... for you race engine owners who use them
as race engines, change yer erl after each track outing.
Also, the viscosity that gives you the least ring pack drag, is SAE30 oil.
All these reasons are why I am biased toward using SAE30 oil in a race
engine. That said, many engine builders use "racing clearances" on main and
rod bearings to increase oil flow. e.g. instead of a main or rod bearing
clearance of 1.5 thou, they do 2.5 thou. They do that to get thick oil to
flow. So, if the engine is built with these greater clearances, and yer
engine man sez "use SAE40" then heed his advice. The principal reason to
select a particular oil viscosity is your main and rod bearing clearance.
Since I am an inveterate cheapskate, when I have had street engines get
well along in life, and I note that the rods knock twice on startup (the
oil flows out of the now loose clearance bearings overnight in the
summertime), or the idiot light comes on at idle, or the idle oil pressure
has been slowly dropping over time, that's the time I remove the SAE30
stuff and put in SAE40 stuff and that cures the problem for a long while.
Several years later, you may change out the SAE40 for SAE50. At this time
start saving your coins for an engine rebuild or trade your vehicle in on
another while it still runs good. You COULD (of course) drop the pan and
stick new bearings in the thing and cure the situation and go back to
SAE30. But then (sich) the thinner oil would flow more down those worn-out
valve guides too!
So ... OK, you try thinner oil and subject yourself to the ridicule of your
friends with race engines who brag about how thick their oil is (the
thicker they run, implies the greater the horsepower capability of their
engine). What do you look for? Well, look for idle and low RPM oil
pressure. If your oil pump keeps the pressure up at low RPM, you should be
OK. Look for high RPM oil pressure. If high RPM oil pressure ALSO stays
where it should normally be, you should be OK. If you have an oil temp
gage, you should see lower operating oil temp with a lower viscosity oil.
One more "thumb rule:" on a race engine your oil pressure should be 10psi
for each thousand RPM of operation. In other words when you have your race
engine built, the oil pump should be selected to do that (or at least in
the ballpark). Note that flow rate is the square root of the ratio of oil
pressure difference (flow at 80psi will be ~1.414 greater than it is at
40psi). A lot of YouRowPeon engines have lousy (by US standards) low RPM
oil pressure. But, I've found that the low RPM oil pressure is normally
over 10psi per thousand RPM. If you run 7,000RPM and only have 50psi on
your oil pressure gage, don't fret too much, you are OK. This is a thumb
rule not a commandment from God. But you would be better off with 70PSI
with that 7K RPM.
single weight oils.
The spec goes like this; for 5W30
The "W" signifies the temperature at which the oil will pour through a
specified diameter hole in a specified time. Or, in other words, is the
stuff a liquid, or is it molasses, or is it tar? Note, to a Chemist,
molasses and tar is a liquid; to an Engineer molasses may or may not be a
liquid (practical folks Engineers are) and tar is not a liquid. So for
5W30, the stuff will pour at 5 degrees F. For 10W30, the stuff will not
pour (to the spec) at 5 degrees F, but it will pour at 10 degrees F. This
spec is to tell you how cold you can get and still (safely) start your
engine.
So, around here in Camelot where it never gets too cold, 10W30 works just
fine. 5W30 or 0W30 isn't necessary. Just stay out of the Sierras in late
January during a cold spell unless you have multi-vis oil.
The "30" is a viscosity, or flow rate spec for "real fluids." So, at normal
oil temps, this tells you the relative thickness of various lubricant
products. Note that the SAE test spec for engine lubricants is not the same
as the one for gear oil, so SAE50 engine oil isn't the same viscosity as
SAE50 gear oil. Usually ... there ARE exceptions (sigh).
Again, note that going up in temperature lowers the viscosity, so (for
example) SAE40 at 230F will have the same viscosity as SAE30 at (say) 215F.
Multi-Vis Dynosour erls use an additive (same stuff STP buys from Chevron)
to create the multi-vis part. These oil molecules are long polymer chains
that roll up into a knot when cold, and unravel , eventually getting almost
rod like when they get hot. Somewhere around 265F, these molecules decide
they've had enough of this rod-shaped stuff and decide to change back into
a knot. What this means, is you take oil with this additive and go up to
Walt Boeninger's Corvette computer limit of 320F, and you've had it; the
stuff flows like alcohol, and you've bought yerself an engine rebuilt. So,
Multi-Vis dinosaur oils should NOT be used at the track if you are one of
those who scoffs at my viewpoint on proper oil temp and blythely runs yer
erl above 250F. The other thing that happens, is these long molecules get
sheared (broken in two) mostly at the lifter cam interface and the stuff
ceases to be multi-vis anymore, and gets runnier at normal engine
temperatures. So, oil DOES wear out in some instances.
Now, to make things complicated, what I said about the multi-vis additive
above, don't apply to synthetic oils. Synthetic oils will tolerate higher
temperature without distress than dinosuar oil. Their viscosity vs. temp.
curve (usually) ususally has a bit slope to it that is different than
dinosaur oil base. The only downside that I know of for synthetics, is they
are somewhat inferior to a good Pennsylvania based oil for extreme pressure
situations, ... like a flat tappet on a cam lobe when you use mongo valve
springs and run astronomic RPMs (above 7,000RPM).
Another interesting thing I have heard from several oil experts (including
the Chief Engineer at Red Line) is that all racing oils "wind up being
SAE20." In other words, thicker oil molecules (which are microscopically
longer) get sheared during operation. And race engine speeds shear lots
faster than freeway speeds. So ... for you race engine owners who use them
as race engines, change yer erl after each track outing.
Also, the viscosity that gives you the least ring pack drag, is SAE30 oil.
All these reasons are why I am biased toward using SAE30 oil in a race
engine. That said, many engine builders use "racing clearances" on main and
rod bearings to increase oil flow. e.g. instead of a main or rod bearing
clearance of 1.5 thou, they do 2.5 thou. They do that to get thick oil to
flow. So, if the engine is built with these greater clearances, and yer
engine man sez "use SAE40" then heed his advice. The principal reason to
select a particular oil viscosity is your main and rod bearing clearance.
Since I am an inveterate cheapskate, when I have had street engines get
well along in life, and I note that the rods knock twice on startup (the
oil flows out of the now loose clearance bearings overnight in the
summertime), or the idiot light comes on at idle, or the idle oil pressure
has been slowly dropping over time, that's the time I remove the SAE30
stuff and put in SAE40 stuff and that cures the problem for a long while.
Several years later, you may change out the SAE40 for SAE50. At this time
start saving your coins for an engine rebuild or trade your vehicle in on
another while it still runs good. You COULD (of course) drop the pan and
stick new bearings in the thing and cure the situation and go back to
SAE30. But then (sich) the thinner oil would flow more down those worn-out
valve guides too!
So ... OK, you try thinner oil and subject yourself to the ridicule of your
friends with race engines who brag about how thick their oil is (the
thicker they run, implies the greater the horsepower capability of their
engine). What do you look for? Well, look for idle and low RPM oil
pressure. If your oil pump keeps the pressure up at low RPM, you should be
OK. Look for high RPM oil pressure. If high RPM oil pressure ALSO stays
where it should normally be, you should be OK. If you have an oil temp
gage, you should see lower operating oil temp with a lower viscosity oil.
One more "thumb rule:" on a race engine your oil pressure should be 10psi
for each thousand RPM of operation. In other words when you have your race
engine built, the oil pump should be selected to do that (or at least in
the ballpark). Note that flow rate is the square root of the ratio of oil
pressure difference (flow at 80psi will be ~1.414 greater than it is at
40psi). A lot of YouRowPeon engines have lousy (by US standards) low RPM
oil pressure. But, I've found that the low RPM oil pressure is normally
over 10psi per thousand RPM. If you run 7,000RPM and only have 50psi on
your oil pressure gage, don't fret too much, you are OK. This is a thumb
rule not a commandment from God. But you would be better off with 70PSI
with that 7K RPM.
Incorrigible said:
I'm still not completely sure, I liked that article though
Nearly baffled me but basically an oil's viscosity determines its ability to flow - a low viscosity flows quickly and a high viscosity flows more slowly.
The W merely denotes Winter and indicates that these grades are suitable for cold climates.
Unless you actually know otherwise that is :-)
I understand the article ....
I'm missing why people call 0w40 "a bit too runny" (I admit to having said this myself)
I was told the 0 and 40 were the relative viscosities at hot and cold. I didn't understand this as a viscosity of 0 clearly makes no sense
If 0w40 and 10w40 are the same viscosities but at different temperatures, couldn't a 10w40 be the same as a 15w50 for instance
Surely the only sensible way of marketing the oil is to have a viscosity/temp curve together with a breakdown specification
I'm missing why people call 0w40 "a bit too runny" (I admit to having said this myself)
I was told the 0 and 40 were the relative viscosities at hot and cold. I didn't understand this as a viscosity of 0 clearly makes no sense
If 0w40 and 10w40 are the same viscosities but at different temperatures, couldn't a 10w40 be the same as a 15w50 for instance
Surely the only sensible way of marketing the oil is to have a viscosity/temp curve together with a breakdown specification
I don't mean to bore you rigid but an alternative explanation can be found at howstuffworks.com
I remember reading all about this when I bought my car - being keen to make the right oil choice
It says:
"The weights given on oils are arbitrary numbers assigned by the S.A.E. (Society of Automotive Engineers). These numbers correspond to "real" viscosity, measured at specific temperatures. Oils that fall into a certain range are designated 5, 10, 20, 30, 40, 50 by the S.A.E. The W means the oil meets specifications for viscosity at 0 F and is therefore suitable for Winter use."
it then goes on to say:
"Viscosity is ordinarily expressed in terms of the time required for a standard quantity of the fluid at a certain temperature to flow through a standard orifice. The higher the value, the more viscous the fluid. Since viscosity varies inversely with temperature, its value is meaningless unless accompanied by the temperature at which it is determined. With petroleum oils, viscosity is now commonly reported in centistokes (cSt), measured at either 40°C or 100 °C"
In respect of multi-grade it goes on:
"At cold temperatures, the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up, the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C, the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot."
That last bit is the interesting bit and is why I have always felt confident that 0W40 was fine as it had good flow properties when the engine was cold (particularly good if you don’t start it up everyday) but when hot it behaved like a 40 oil which is plenty thick enough.
As you say, there are some very experienced and brainy people on here who don’t like 0W40 saying it is too thin. To me that must mean at normal oil temps the oil behaves more like 0 than 40. I have to say I have noticed my idle oil pressure drop in the 2 years I’ve been using Mobil1 so will change to 15/50 next time.
I remember reading all about this when I bought my car - being keen to make the right oil choice
It says:
"The weights given on oils are arbitrary numbers assigned by the S.A.E. (Society of Automotive Engineers). These numbers correspond to "real" viscosity, measured at specific temperatures. Oils that fall into a certain range are designated 5, 10, 20, 30, 40, 50 by the S.A.E. The W means the oil meets specifications for viscosity at 0 F and is therefore suitable for Winter use."
it then goes on to say:
"Viscosity is ordinarily expressed in terms of the time required for a standard quantity of the fluid at a certain temperature to flow through a standard orifice. The higher the value, the more viscous the fluid. Since viscosity varies inversely with temperature, its value is meaningless unless accompanied by the temperature at which it is determined. With petroleum oils, viscosity is now commonly reported in centistokes (cSt), measured at either 40°C or 100 °C"
In respect of multi-grade it goes on:
"At cold temperatures, the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up, the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C, the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot."
That last bit is the interesting bit and is why I have always felt confident that 0W40 was fine as it had good flow properties when the engine was cold (particularly good if you don’t start it up everyday) but when hot it behaved like a 40 oil which is plenty thick enough.
As you say, there are some very experienced and brainy people on here who don’t like 0W40 saying it is too thin. To me that must mean at normal oil temps the oil behaves more like 0 than 40. I have to say I have noticed my idle oil pressure drop in the 2 years I’ve been using Mobil1 so will change to 15/50 next time.
IMHO 0w is a figure for marketing purposes, as you say a viscosity (thickness) off 0 has to be non existant. But it is the ultimate claim when selling your high performance oil!
The first figure always refers to the visc at Zero degrees F and the second figure refers to the visc at 210 degrees F.
Its all about marketing these days - a lot of profit in fancy oils!
The first figure always refers to the visc at Zero degrees F and the second figure refers to the visc at 210 degrees F.
Its all about marketing these days - a lot of profit in fancy oils!
neilmac said:
IMHO 0w is a figure for marketing purposes, as you say a viscosity (thickness) off 0 has to be non existant. But it is the ultimate claim when selling your high performance oil!
The first figure always refers to the visc at Zero degrees F and the second figure refers to the visc at 210 degrees F.
Its all about marketing these days - a lot of profit in fancy oils!
SAE 0 is just a number allocated to a viscosity - it is not the "real" viscosity which is measured in cSts. So you can have an SAE of 0.
The measured temps are 40degC and 100degC. 0degF is -18degC (very very cold!)
Edited to add: If you are a engineer specialising in these things I take back everything!!!
>> Edited by GarryM on Wednesday 3rd September 15:49
GarryM said:
IMHO 0w is a figure for marketing purposes, as you say a viscosity (thickness) off 0 has to be non existant. But it is the ultimate claim when selling your high performance oil!
The first figure always refers to the visc at Zero degrees F and the second figure refers to the visc at 210 degrees F.
Its all about marketing these days - a lot of profit in fancy oils!
The measured temps are 40degC and 100degC. 0degF is -18degC (very very cold!)
Sorry, yes I was getting my Fs & Cs mixed up!
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