Oil for 964?

[clockworks]

I need to top up the oil on my 964 - just below halfway on the dipstick and gauge when stationary and hot with the engine running.

What grade is normally used, and is it fully or semi synthetic? Car was last serviced by the previous owner at an OPC.

Would it be OK to top it up with some Mobil 5W-30 fully synthetic? I can a few litres of this for an extremely good price.

[boxsey]

You will probably get a lot of varying opinions about what to use. 5W-30 is too 'thin' at operating temperature and AFAIK is not on the Porsche approved oils list. I use 5W-40 synthetic which is more viscous at operating temperature.

[davek_964]

Take care you don't overfill too - you can screw up the idle if you do. About 1/2 to 2/3 on the gauge is about right (warm idling, etc. etc). Once it's down to about 1/3 I'd top up but probably not before that (hardly ever had to top mine up).

[boxsey]

Excellent advice from Dave! I wouldn't top up either if it's reading halfway.

[clockworks]

I'll be careful not to overfill above halfway.

The handbook that came with the car lists loads of different grades, from 5W-30 to 10W-40, as well as saying semi and fully synthetic are OK, and to consult the dealer.

Is it OK to mix semi and fully synthetic? I've no idea what was used when the car was last serviced.

[ras62]

As already stated you do not need to be topping up the oil on a 50% reading, there is plenty of oil in the system even when the reading is at a minimum. 5w40 to 10w50 seem to be the most common oils used.

[sneaky schnell]

I use 10W-40 and agree with other posters about taking care to avoid overfilling.

When I first had the car, I used to always check both gauge and dipstick but I have since learned to trust the gauge.

Mine doesn't use much but I always keep a litre in the boot, even if it ends up going into the OH's car.

[clockworks]

WRT mixing semi and fully synthetic, I spent a while googling the subject. Mixed views, but a popular one is that semi is a mix of fully synthetic and mineral, so you can mix anything you like. It's safe to add fully synthetic to anything, but adding semi or mineral will "degrade" fully synthetic proportional to the amounts. Makes sense, so I'll go with that.

Just got back from a run, and the gauge is actually halfway between red and half full, so I'll put half a litre in.

I bought the last 5 litres of that Mobil 3000 5W-30, as it was crazy cheap - £2.25 in total! I'm sure it'll come in useful eventually.