10W40 vs 15W40

That's 2000 miles to every litre. I'm amazed that you can feel the difference unless your engine is meant to run on thinner oil still.

I haven't noticed the

What does your good book recomend?

Why do you think this? Maybe you think far too much?

Nope

Whether it needs it or not.

Huw

There is no difference between the oils when the engine is warm, then both oils perform as a grade 40 oil. The difference is when the oil is cold at start time, then the 10W40 is clearly better; it will flow around the engine sooner. To prevent head gasket failures, you should always drive the car gently until the engine has reached full operating temperature.

It's probably causing the hydraulic tappets to be lazy when it's cold.

It's your choice really, thicker oils will tend to burn off less, but of course will increase resistance in the engine. Thinner oils will burn off more, but give better performance and economy. Personally I never noticed any difference in performance overall, only in the amount consumed.

Any make will do as long as it meets the minimum specifications, anything from a 5/30 to a 15/40 will not do any harm.

No.

No, these are prone to that whatever you do. Sitting in heavy traffic is what seems to cause it.

Yes, I read the text before replying, would have been better to mention that at the top :-)

You went the wrong way. 0w40 would be better as that gives you better cold start protection. You will have more wear now rather than less

Oil is the same thickness when hot, so you were probably losing it in the warmup cycle as the new oil is thicker then.

What the manufacturer recommends

No unless you fill it with sand.

Only if it runs out of oil

Ask your Dad!

[snip]

Why oh why did you change to a thicker oil just in time for the winter?

Anyway, your handbook should be referred to.

I was changing to see if my car consumed less oil, and it does. I didn't think the difference in performance would be noticeable :(

The manual says one thing and Fiat says another lol. My manual recommends 15W40 Selenia, Fiat recommend 10W40 Selenia, and I don't think they sell 15W40 Selenia anymore. I think my next load of oil will be Selenia (unless I sell my car first), and I change it as soon as we start getting some warmer weather (probably in about 3-5 months time).

It is not all that important, you can use anything from 0W40 to 15W40. The lower the first number, the better cold starting properties.

However, 0W40 contain more multi-grade additives than 15W40 as the oil span a larger grade range. In some warm countries, this may be unnecessary, so they use 15W40, in particular if it's a commercial vehicle that is running a lot for every cold start.

The fact that it is noticeable should tell you that their are large pumping losses in a cold engine which means that the oil when cold cannot get round the engine properly. As Dervman says - just in time for winter when you do not want a thicker oil as the colder weather will just exacerbate the situation even more.

It doesn't actually. The 0w/40 is guaranteed to be synthetic which is a more naturally thermo stable base so it needs less work done to it to span the scale index. The 15w/40 is almost certainly a mineral oil. It is unusual for any manufacturer to specify a 15w/40 oil for use in a petrol engine these days. It is the overwhelming choice for most diesel engines. It should be noted that a whole range of oil viscosities are suitable in any particular climatic condition so the best choice is one that is suitable for both Winter and Summer use for both cold starts and prolonged heavy use in viscosity terms and, in a petrol engine, at least API SL or a performance grade one up from the minimum specified by the car manufacturer if that is better than API SL. That does NOT mean a semi synthetic where a mineral is specified etc. It means one performance STANDARD up from the minimum.

If in doubt, RTFM and use the latest equivilent of the manufacturers recommendation and sleep easy.

Huw

I would have thought your manual would give you a choice of viscosities pertinent to different ambient temperature ranges, but there you go, it is a Fiat. They will certainly not restrict you to Selenia oil and will specify a minimum standard which an oil has to meet to be suitable.

Huw

0W40 apparently isn't a great idea on these 'thrown together' Fiat engines.

IIRC it specifies a 15W40 semi-synth.

Fiat engines are not thrown together. In fact Italian engineering is state of the art. Their electrics are another story, though much improved over the last six or seven years.

0w/40 oil in general and Mobil1 in particular is far too good to be used in standard engines with short service intervals though. You could use it but you would be throwing good money away. Use what they recommend in the book that came with your car

Huw

I doubt if it specifies that. Why not actually check instead of guessing?

Huw

>

Its more likely to be the oil pump absorbing more power trying to pump a thicker oil aroumd, especially forcing the considerable excess through the pressure releif valve....

Obviously the smaller the engine the more noticable the effect.

Tim,,

LOL, I doubt very much if it would make that much difference, if it did it would most likely snap the cambelt first.

I don't think I've commonly seen a 15w40 semi synth? Normally

10w30/10w40/15w40 mineral/enhanced mineral 10w40 semi synthetic 5w30/0w40/5w40/5w50/10w60 full synth.

I know other weights are available but not common as those listed.

It probably didn't come with a book, they forgot to put a rev counter and temp gauge in, surprised they remembered the steering wheel.