what oil do you use?

biggsy

biggsy

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Jul 4, 2008
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Ok guys, I am going to go synthetic engine oil whats your opinion? I serviced the trans and added Tran-Synd I bought at an allison shop for 8.63 a quart! The GM dealer wanted 18 BUCKS! A quart. I want to go synthetic engine oil. I live here in sunny Ca temp has been 95 average so i think i will use 5-40 any advice on brands or viscosity? thanks to all
 
5-40 is too thin for the hot summers with these engines IMO. The oil pressure drops too low when hot at idle.

ben
 
this subject has been debated many times, but it has been upheld by some of the oil distributors that a lower viscosity oil such as 5w30 can cool more effectively because it flows more volume than 15w40 even at higher ambient temps. but with that said, some of the dmaxes do run to low on idle oil/psi. if i had below 20 psi at idle i would not use 5w30. i'm in socal and i use delo 15w40, dino no problems. i paid 36 bucks a gallon for transynd! i am running that in the trans. mobil synthetic is very good for the price, but don't use the mobil 1 for cars! mobil delvac 1 synthetic 5w40, much better than rotella synthetic.
 
Be sure your synthetic is a group IV synthetic. Most oils that market themselves as "synthetic" are just group III hydrocracked mineral oil base stocks, not PAO base stocks like a group IV oil. Valvoline, Mobil, Castrol, Shell, and other synthetics from companies that have their investments in crude oil refining are just group III products. AMSOIL is a pure group IV synthetic. There are also Group V ester base synthetics like Redline. Group V oils aren't as well suited for extended drain intervals or heavy duty use. Group V oils are better suited for factory intervals or shorter term use. Group IV oils are the best for diesels, extended drain intervals, and hard use.

-Chuck
 
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