I just wondered if using a good oil in a TDI engine would result in longer term economy benefits... Its just I've been using Millers XFE-PD oil for about 25,000 miles now, and although general performance is unchanged, I seem to have it in my head the car is a little less economical. :confused:

Is there a general rule that using the best oil in your engine will give better returns on economy, so therefore spending extra on dealer "good stuff" could be reaped back at the fuel pump?

Just wondering... I only got 37mpg on a 80mph trip back to see my Dad this evening, although the route involved an overall sea-level to 250m above climb.

In my own experience, the viscosity of oil will have a small (up to 2mpg) effect on overall fuel comsumption. e.g using a 10w-40 oil will cause a slight increase in fuel consumption compared to a 0W-30.

There may be a slight difference between different brands of the same nominal viscosity, but I doubt that you'd notice any difference in fuel consumption.

Ambient temperature will also effect fuel comsumption: in winter, the oil will be thicker (more viscous) when starting from cold (and the engine will take longer to reach operating temp) which will require more energy to pump round the engine - i.e more fuel being burned. You'll probably see a small improvement in fuel consumption when the weather warms up.

The thinner the oil the higher the mpg will be, it will never go through the roof but that is half the reason why many VAG cars are running on 0w-30 to help meet mpg regulations.

Cheers

Guy.

And many other makes also, including F*rd.

The question you should be asking is not "is it cheaper" or "is it synthetic" or even "will it make my car more economical" but "DOES IT MEET THE REQUIRED SPEC" (IMHO of course)

True, the specs are by far the largest confusion over VAG oils, they are releasing an oil to cover all of the specs, no matter what spec you need, have not got an idea on cost yet but will keep you posted as and when.

Cheers

Guy.

Well, I thought the 5w-40 was the only thing we're supposed to be putting into our PD TDIs. :confused: Are F*rd using 0w-30?

5w-40 goes into your pd engine because it does not have the variable service option, unlike the Octavia, which can then use the longlife 0w-30 oils.

Ford use 5w-30 at the moment but are going thinner over time.

Cheers

Guy.