5w40 vs 10w30 in turbo volvo

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Oct 11, 2002
Surrey BC
HiI'm new to this site ,but have been reading tis for about month now , anyways what I was going to post is how different vis. affect engine performance . Since graduating as auto tech. and working back in europe for Fiat in their racing div. I do know thing or two about engine performancce . So I have hooked up vacuum/ boost gauge on my volvo 850 turbo , yesterday I chenged engine oil ,went from Chevron delo 400 5w40 gr III , to nascar synthetic 10W30gr IV and V blend and instantly gain 2inhg of vacuum which is pretty significant,. How good this oil is ? I have no idea but reduces friction inside the engine I'll keep ti in for 5k and change it , this is my plan , Eric
Isn't there a difference in drag between the 40 wt. oil and the 30 wt. oil in the turbo bearings? Isn't that restrictiong the turbo's rpms and therefore the vacuum/boost?

That's very interesting. Let us know if there is a noticable performance or mileage difference.....an oil analysis would be great too.

I've been considering a 5W-40 or 0W-40 Mobil 1 for my '02 S40. Dealer says use 10W-30, service book says 10W-30 is good up to 104degF, but the owner's manual (printed by Volvo in Europe) says use 5w-40 for a much wider temp range than 10W-30 which is not reccommended over 86degF....how is that for conflicting advice??

The oil specs for most engine are written with the assumption that you are going to be using an average quality, or even below average quality, petroleum oil. I have found with Amsoil that you can generally go one SAE grade thinner than what the engine manufacturer recommends in a petroleum product. Running the low viscosity synlube reduces your oil temps, so the oil doesn't thin out as much. In addition the film strength of PAO/Ester synthetics is significantly higher, so you don't need a thick oil to get excellent wear protection. I have been using and recommending this approach to my customers for the past 17 years in a variety of applications.

Mobil 1 is an excellent synthetic oil for the price, but I'd actually go with their 0w-30 for the best performance in your Volvo. At operating temp, the Mobil 1, 0w-30 is about the same viscosity as the Amsoil "XL 7500", 10w-30 you have been using ....It will work fine in your engine.

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