Ask an expert

The engine currently has 10w30 engine oil which is the grade specified .
I have used Castrol Magnatec 10W40 in my previous cars , so would this be ok to use in my Fairmont ? . Would it affect fuel consumption to the point I would notice a change ?

Although it is expensive I would use Castrol Edge 5W30 if that was the best option .

Thanks

It would be very doubtful that changing the grade of oil will give you a noticable improvement in fuel economy.
The Castrol Magnatec 10W40 has a good reputation as a good quality oil, so there's no reason why you can't use it, but only because it's a good quality lubricant, not for reasons of any noticable fuel consumption improvement.

Thanks . I was approaching fuel consumption from the angle that using a 10W40 grade oil instead of 10w30 may increase fuel consumption slightly , as when hot, 40 is a bit heavier than 30

I agree that Magnatec has a good reputation and have used it exclusively in my cars for about 9 years.

OK, I see what you mean. However, it's doubtful that a small change in oil grade will make any difference either way in fuel consumption.