Shell Rotella T6 15W40 vs Mobile One 10W30
 

So what oil are you guys running? I was using Rotella T6 15W40 for the ZDAP. After a little more thought I switched to Mobile One 10W30 because I feel the 40 may be a little to thick. What are your thoughts on this?

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

Either or, they both are good for your engine, just remember to change it every 500 miles.

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

With a full flow oil filter I tend to go a bit more than 500 miles.

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

Ron,


in this case, a viscosity 15W-40 is the better one.

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

FWIW, Ron Ehrenhofer, the Technical Advisor for MARC's Model A News uses Mobil 1 10w-50. I use Mobil 1 10w-30.

From everything I have read, the zinc is not necessary for cars of our vintage. Ideally, I would use Mobil 1 10w-40, but it can be tough to find these days. As many have commented over the years, just about any oil available today is better than what was used back when the Model A was new. Our understanding of oils and the technology of oils have changed significantly, so what was accepted back then is probably irrelevant today. Modern cars use 5w-20 and can run for over 200k miles easily.

As to oil change intervals, who knows what is best? 500 mile changes isn't going to hurt anything, but that was back in the day of non-detergent oils and dustier roads.

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

Ford's original Instruction Book (Owners Manual) said to use SAE 40 oil in the summer and SAE 20 oil in the winter. So the 15W40 oil is pretty close to what they called for. So is 20W50. The 20W50 oil is probably better for an older engine that tends to burn oil. Either one is close to what Ford called for.

In South florida, where there is no winter, really, I used to run straight SAE 40 oil all year round. But it is easier to find the 15W40 today than it is straight 40.

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

Rotella T1 SAE30 straight weight @ Walmart

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

Don't forget the A has a splash and drip oil system - not a pressure one. The 40 may be too heavy to easily lube the rod bearings and flow too slowly to make the mains happy. A looser engine could use the 40 weight to better cushion the babbit. Longer lasting insert bearings should probably stick with 10-30w. I'm not sure if the cost of synthetic is justified at the recommended 500 mile change rate. And yes the valve spring pressure in an A is so low you don't need to add zinc.


Understanding viscosity - https://blog.amsoil.com/understanding-oil-viscosity/
New engines have tighter tolerances and were designed for oils like 5-20 - mainly as an fuel economy move to get the EPA numbers up. When the Chevy ZZ4 high performance crate engine came out a lot of people felt the factory recommended 10-30 was too light so they went with straight 40 and suffered bearing failure because the rod side clearance was very tight and would not allow the oil to flow out fast enough so the oil stayed around the bearing too long, got hot and burned causing the engine to fail.

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

It is my understanding that the 40 in 10W40 means it acts like 40W when hot. To me that means that it is pretty low viscosity when hot and why I am happy using it.

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

Bruce is right. The oil has a viscosity of 40 when hot. It if it is a multi-weight oil it actually thickens to get to that viscosity, and a viscosity of 40 when hot is pretty flowable. One of the things we don't seem to focus on is that the oil in an A with a 160 degree thermostat probably never gets hot enough to thicken to a viscosity of 40 (let alone 50), because the thickening agent is not hot enough to fully work. If anyone can address this point I would like to see some info....but please don't hi-jack this thread. Thanks.

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

I must be mistaken as I thought the Model A was originally filled with straight 30.....If 40 is the case Shell Rotella T6 15w40 wins :D

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

Since I have a slight leak, I use a good quality but inexpensive oil that I can afford to change more often. I found 10w-40 oil at Atwood's Farm & Ranch for $3.99/qt. Good value for the money I thought.

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

Maybe hear in Carolina Rotella T6 15W40 would be a better summer oil and Mobile One 10W30 for winter.

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

See attached scans from a late-1931 Ford Model A Instruction Book (it shows the indented firewall and fuel valve under hood).

Full disclosure, my 1929 version of the Instruction Book does not have these words about S.A.E. 40 oil in summer. Ford added them to the book in later version.

So that's my basis.

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

Multi viscosity oil such as 10W40 has the flow rate are of 10 weight and the film strength of 40 weight. All oil thins as it warms.

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

Good Morning all...Jim is correct. The original owners manual...which was written by folks in Detroit where it is cold in the winter and warm/hot in the summer, calls for 20wt in the winter and 40wt in the summer. That's what the design engineers expected folks to use. Possible modification if you have an old loose engine. I live in Scottsdale, Arizona and the fellow who built my engine (John Cook) and many others around here believes that 30wt works best for how he built the engine in our weather. Checking with your engine builder is best if you know who did the work. Ernie in Arizona

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

I did not know the viscosity language above is in the onwers manual. Very interesting.

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

Hey Jim
I did use Mobile one 10w30 on the Phaeton over the winter but I am going back to Shell Rotella T6 15w40 next oil change. I know your Dad restored the Phaeton and rebuilt the engine but how many miles would you guess he put on it since he got it in 1975? The car now has new radial tires, an oil filter and a Mitchel so I am planning on putting on some miles this year. Car drives effortlessly at 55 so any long trip on a 2 lane black top is not going to be a problem. On a different note I am also restoring a 31 Victoria that I have original paper work on since sold new in 32 all the way to the last registration in 1950. She is now in pieces but my plans are to go fine point shooting for 400 plus points.

Ron

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

Hey Jim
I like to think I am taking good care of the 1929 Phaeton so below is a photo of her as of 4/20/2023. Just a beautiful example of a very good driver that is very much loved.

Ron

Re: Shell Rotella T6 15W40 vs Mobile One 10W30
 

I would guess 15-20,000 miles are on that engine. He drove that car a lot.