Oil and Additives

[Guest]

I have recently sorted what potentially would have been a very expensive problem by speaking to an OPC and being told that even thought the manual suggests that 10 - 40 oil is the correct to use that actually 15 - 40 is recommended.

I used 10 - 40 and the engine started knocking at certain revs.

After a full oil change and replaced with 15 - 40 Semi Synthetic, the engine knock was gone.

Can anyone recommend any oil additives that may help too?

 

[bones]

Phil glad the knock seems to have gone but like you probably I find it hard to believe an engine noise is cured by changing the operating range of the oil. I've helped gearboxes perform better and make them last a little longer by trying different oils but never an engine. Maybe the effect of the new oil is masking the knock for now, keep us posted. What is the make of oil?

 

[oliver]

The very low viscosity oils (0W or 5W lower range) can seek out and create oil leaks and once established are impossible to prevent. Older cars should, ideally, only go down to 15W.

 

[Guest]

Not tried it myself, but I know of some 3.2 owners who have tried Slick 50.

How frequently do you change your oil?

 

[Melv]

If you buy a decent name brand oil, you do not need to use additives. (Source: Porsche visit to Castrol test centre at Pangbourne). Where, incidentally, they use a 911 engine on a comptuer test cycle because the tolerances are so good. If they measure wear, they know it's the oil, and not the engine....

Try Mobil 1 Motorsport, recomended for older engines with bigger oilways. The low viscosity 0w oils are designed for modern engines with small oilways. (Source: Mobil rep at Goodwood FOS.)

Mel

 

[oilyrag]

I have used 0W 40 synthetic in a '72 911 2.4S engine for over 4 years........no funny noises either before or since engine rebuild.
Also you are only quoting the cold viscosity as being different.......the high temp viscosity you are quoting is the same ie SAE 40 ...in other words both 0W 40 & 15W 40 are the same thickness at engine temp.
Does your car have hydraulic chain/belt tensioners or valve adjustment?
This is a possible source of the noise but more particularly at cold engine temp.
Avoiding additives is always a good thing unless you have a severe problem that cannot be solved in any other way or are just trying to get an engine through to the next major overhaul (putting off the inevitable for a few months)....they can cause more problems than they cure[8|]