Re: 30w oil
 

I do understand the W for a 10W40 multi viscosity oil, 10W is for Winter.


I thought when you are talking about a single oil like the old SAE 30 ford oil, it was called weight. 30 weight, oil that is not modified. If not referred to as weight what is the proper term for it?

Re: 30w oil
 

Winter is a subjective term, depends on the particular region one lives in. When I think of winter I think of down to -30F or -40F.

According to: https://www.usclimatedata.com/climat...tates/usmi0220
It doesn't even normally get down to 10°F in Dearborn in the winter, so 20W is fine if one lives in that region.

Re: 30w oil
 

that is very old world thinking. just like the guys who tell you to use non detergent oils . why? if your engine is in good shape and bearings and rings tight, lighter oil flows better, and protects better than heavy oils with less chance of burning

Re: 30w oil
 

Gasoline engine oils from API SC upwards contain additives that attack non-ferrous metals (bearing bronze) and white metals in the plain bearing shells of the crankshaft and connecting rod. Therefore it is better to use API SC.

This has nothing in common with the viscosity!



But the large tolerances of old engines always need a relatively thick oil. Multigrade oil is good. But not with too low base viscosity! Every oil - even multi-range! - becomes thinner with increasing temperature. A multigrade oil only becomes "slower" thinner. Therefore, 10W-XX is less favorable for these engines than 20W-XX.

I worked as a consultant in the lubricants industry and have my own mix: SAE 25W-50 in class API SC.

Re: 30w oil
 

Before the addition of the"W" designation, oil was catagorized by its SAE number (usually abbreviated as No.). For example, S.A.E. 10 or No. 10, etc. The term "straight" was also used; as in "Straight 10".

As refining methods improved, it became possible to produce an oil that had identical hot viscosity as No. 10 oil, but would flow at a lower temperature than 10. S.A.E. created the "W", or "Winter" designation (10W, 20W, 30W, etc.) for these oils. You can find charts online that give the temperature ranges for each viscosity.

Re: 30w oil
 

mine has run happily on diesel grade 15-40, 15-40 synthetic and now 10-30 synthetic. modern oils are so much better that I don't really think it matters very much what you put in it

Re: 30w oil
 

Wear happens with cold, thick oil.


At no point in normal operation will a 0W-40 get thinner than the SAE40 - they are both the same viscosity when hot, which is when they are the thinnest.


They BOTH thicken as they cool.



A 0W-40 works better than a SAE40, because it thickens less when cold - they're both as thin as each other when hot though. The difference is that the 0W will flow better cold, giving the best of both worlds.



It's a somewhat moot point though - not too many people are going to pay for 0W-40 and dump it every 1000 miles though!


Ours usually runs a 15W-40, more for cost/availability than anything.


How many model A owners even drive enough miles for the oil to impact the engine longevity anyway??? ;)

Re: 30w oil
 

x2 - You did a much better job of describing what I was trying to say.

Re: 30w oil
 

This makes sense to me but I remember reading in the owners manual for my Jeep that 5w-30 is only recommended for sustained temps below freezing AND that using 5w-30 in higher temps would lead to an increase in oil consumption compared to the 10w-30 recommended for above freezing use.

If they both flow like SAE 30 when hot (which they should), why would oil consumption change?

Re: 30w oil
 

Shell Rotella SAE30

Re: 30w oil
 

most common sense answer ever, put into words all can understand.