RxFX101

oops..haha..missed that!

repeater

Maybe so. Sounds right :-)

YucatanAudi

"effective weight", while the upper number denotes the maximum protection.

I've been told (so, take this with a grain of salt?) that "weight numbers" only truly apply to petroleum-based oils. Thus 15w-50 would have at least the Flow Characteristics of 15w petroleum oil, while protecting your engine up to what a 50 weight oil would do - knowing that heat thins petroleum oils.

So, synthetic oil can be "thinner" because it gives higher temperature protection without thinning or breaking down into petroleum components. Or so they say.....

SteveAngry

the Shell Rotella Synthetic? It's a 5w-40 synthetic oil and costs $12.99 for a large jug.

I'm using this for winter oil.

It's been highly recommended.

Mobil 1 is great, but I'm getting sick of shelling out nearly $30 every oil change...

Steve
Michigan

Merkin

does it matter? synthetic > dino

YucatanAudi

and is less susceptible to losing lubricating properties when very hot. That's why you'll find it used by airplane engines and race teams.

For a street car, I think if you change the oil regularly - 3000 miles tops - you'd always be fine with petroleum oil. (Castrol non-synthetic is actually made from the vegetable oil of the Castor Bean and is a very good oil too!)

But if you have a hot running engine, race a lot, or long hot highway trips, synthetic may be better.

Personally, I always use synthetic. For smaller engines, I have found that the lower friction really smooths things out. I've put over 140,000 miles on an engine without any engine problems or oil usage by using synthetic faithfully since new. 1st car sold at 144,000. Next car, sold after 87,000 miles. Current car has 124,000. etc.

Merkin

i do 10k changes using oversize filters

Audilard

12 quarts at Costco = $23!! 6 quarts of fully synthetic = $22

repeater

Seen it - but not tried it.