Oil

Author
Discussion

RCA

Original Poster:

1,758 posts

220 months

Wednesday 16th January 2002
quotequote all
Ok I need some advice, Having owned my TVR now for about 4 weeks it needs a little bit of oil, it has been very good so far!!! I rang the garage that last serviced it, the only non TVR service!!!, it was a Lotus garage so I thought not bad! They think that they put 10 - 40 semi-sinthetic oil in but not 100 percent sure, What do I put in?, I know that some oils do not mix, do I go along with the 10 - 40 and hope that they are right ????

plotloss

67,280 posts

222 months

Wednesday 16th January 2002
quotequote all
Recalling from memory, so this could be horribly wrong, it depends on the mileage. Its something like

0-1000 miles Mineral Oil
1001 - 6000 miles Semi Synthetic
6000+ Fully synthetic

Mobil 1 at all times is recommended.

Matt.

RCA

Original Poster:

1,758 posts

220 months

Wednesday 16th January 2002
quotequote all
I would like to put mobil 1 in but due to the fact that they have probably put 10 - 40 in I can't, or can I?

plotloss

67,280 posts

222 months

Wednesday 16th January 2002
quotequote all
I'm not sure to be honest, 10-40 refers to the weight of the oil at specific temperatures. The 40 meaning that its not too viscous at cold tempratures and the 10 meaning that it doesnt lose all its viscosity at high temperatures. Or it could be the other way round.

I dont see that mixing two different brands of oil, providing they are both the same 'weight' could do much harm, but I am not mechanical expert so I could be completely wrong.

Matt.

Dan Myers

278 posts

235 months

Wednesday 16th January 2002
quotequote all
Standard Mobil 1 is 0w40 but Mobil Motorsport is 5w40 so it is better to use on the Rover V8 and Halfords do it at about 35.

I believe in mainland Europe Mobil also sell a 15w40 Motorsport oil, which is still cheaper than the standard stuff here.

Last time I got some in France it was 15 for 4 litres of 5w40.

Regards, Dan M

GarryM

1,113 posts

235 months

Wednesday 16th January 2002
quotequote all
quote:

Standard Mobil 1 is 0w40 but Mobil Motorsport is 5w40 so it is better to use on the Rover V8 and Halfords do it at about 35.



If thats the case why would TVR recommend Mobil 1 0w40?

IainS

11 posts

223 months

Wednesday 16th January 2002
quotequote all
The best oil for these cars is Castrol GTX Magnatec. This keeps the cams etc very well lubricated especially on startup. The engine will be much quieter.
This is used on many of the race cars ie Tuscans etc.
Mobil 1 is a bit of a myth, more of a 'commodity' probably commonly used because it's expensive!

russell

27 posts

236 months

Wednesday 16th January 2002
quotequote all
quote:
I know that some oils do not mix, do I go along with the 10 - 40 and hope that they are right ????


As I understand it, you can mix different weights/grades of oil but you should not mix minerals with synthetics.

Russell

jellison

12,802 posts

229 months

Thursday 17th January 2002
quotequote all
Mobil 1 Motorsport is 15/50 over here to - this is what I am putting in mine next week for it's 30k serv at TVR Dealer - I supply it - Should be thicker when hot and hopefully not get used at such a high rate as the super runny 0/40 current std Mobil1. CHIM500

ATG

16,501 posts

224 months

Thursday 17th January 2002
quotequote all
I am confused about this. From the way they are priced I would assume that the more fluid the oil is, the better ... hence 0w40 is better than 15w40 or whatever. If there is less internal friction in the oil (i.e. it is more fluid) then I assume it follows that it is a more efficient lubricant. The downside is that it can flow through smaller gaps so you will loose/burn more of it.

THe magnetex oil is supposed to cling to metal so that the oil doesn't drain out of the top of the engine when the oil isn't being circulated and therefore reduces friction when you start the engine.

Have I got the wrong end of the stick? In particular, why would 5w40 be better than 0w40?

cockers

600 posts

233 months

Thursday 17th January 2002
quotequote all
I would have thought thin was best at start-up, especially at this time of year ands that thickness when hot wasn't such an issue given that these engines aren't especially high revving.

Depends what you mean by "hot", I suppose. And how you drive your car - mine only gets short blasts at highish revs, because that's the way of British roads and I don't do track days.

Maybe I'm lucky, but my car hasn't lost a drop of Mobil 1 in nine months and there are no deposits on the back of the car.

I shall be sticking with it unless I hear compelling reasons not to.

zippy500

1,883 posts

221 months

Thursday 17th January 2002
quotequote all
I was told by a mobil dealer, motorsport stuff is meant for superbikes but is good for cars that do track days, hence using more of the cars perforamnce and runing hotter, the higher viscosity will then give better protection when blasting down the straights etc. If you only use the car on the road and drive it like the previous posting and like I do, Mobil 1 is the one too have. However, I must add, I considered motorsport as last summer I got caught in a 5 mph motorway crawl for 2 hours. Although the car never overheated it knackered my oil and possibly motorsport would have handled this a bit better. I am still running on Mobil 1 for the record.

As for mixing semi synthetic and mobil 1. I would personally drain your oil and replace it all. I used to work in an oils and fuels laboratory and during investigations sometimes found these 2 types of lubricant not to mix as well as suggested on the can.

ATG

16,501 posts

224 months

Thursday 17th January 2002
quotequote all
Ah hah. Interesting. I hadn't thought about the oil's resistance to high temperatures.

I once conducted an experiment with some engine oil and a blowlamp in an attempt to calibrate an oil temp sender. (This wasn't very sensible, I know). Its really amazing how much the viscosity changes. I was using cheapo oil. Started like treacle and ended up like water. God knows what Mobil 1 is like when hot.

yum

529 posts

225 months

Friday 18th January 2002
quotequote all
So... it's all clear then.

martvr

480 posts

223 months

Friday 18th January 2002
quotequote all
Did somebody ask?
Part 1.
Skip most of this rambling if you want, the conclusion starts in the third last para. in part 2 .

One of several lubrication needs within the engine are the white metal bearings, as on the crankshaft for instance, which need a film of oil between the rotating metal surfaces at all times the engine is running to prevent metal to metal contact and disaster. This is ensured by maintaining oil pressure within the bearing.

The factors acting to reduce the film thickness are:

1. Low supply pressure
2. Excessive clearances in the bearing
3. Thinness or viscosity of the oil
4. The load applied to the bearing

1. is obvious
2. will allow the oil to exit from the bearing too readily and reduce the film thickness
3. the thinner the oil the faster it exits, same effect as 2. Selection of oil grade (0W40 thinner than 15W50 for instance) and oil temperature then important as lower viscosity and higher temp. both thin the oil
4. the duty expected from the engine e.g. during racing will increase the load on the bearing and this will reduce the oil film.
Cont.

martvr

480 posts

223 months

Friday 18th January 2002
quotequote all
Part 2
Apart from disastrous failure at the extreme, the wear rate of the bearing dramatically increases as the film thickness reduces towards metal to metal contact.

Oil selection is a compromise in order to best suit all operating conditions and functions but should consider first and foremost the lubrication requirements of the engine. The oil also carries out other functions such as cooling, containment of contaminants, anti-foaming, anti-sludge etc. Unfortunately using a thicker oil increases the friction losses within the oil which itself raises the temperature so the selection of a higher viscosity oil is not necessarily a universal gain.

The usage of the oil as it leaks past the pistons, valve guides etc. is therefore secondary and it will be what it is for any particular engine, dependent on clearances, duty, temperature etc.

In the absence of greater experience (mine) I take a trusting view and assume that the engine designer has done his calculations correctly including allowing a good margin of safety and I am persuaded to follow his recommendation when it comes to oil. It is that design margin that allows a bit of tolerance in oil selection but it is there mainly to accommodate for oil deterioration with time, varying engine condition and duty and most importantly to ensure a long (engine) life. You won't necessarily see the effects of increased wear caused by the wrong grade of oil for quite a while.

IMO only if the engine is subjected to a very arduous duty such as racing, very high ambient temperatures etc. is it worth considering changing and then only with advice from a reliable source. A very badly worn engine that is displaying low pressure could perhaps live a bit longer with a thicker oil though.

Apologies for the length, if you got this far, hope it helped or maybe I just made it worse.