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Switching from Amsoil to Mobil 1 question

C clockworkMember
I hope this has not been covered before..........I did search the forums for the answer and came up empty handed.

I have a 72' pantera which I recently inherited from my father. The vehicle sat for almost 2 years without being started. I pulled the plugs, sprayed some mystery oil in each cylinder (thanks to you guys for the advice), ran the motor and fired her up. Fired up like it was never sitting and took her for my first drive ever. Enough rambling.....

My dad was running amsoil 10w40 which served him well for the amount of time that he drove it(which was very seldomly, and in moderate temps around 55-80 degrees F). I intend to run the car more often and from early spring (now) to the height of summer (and into fall). I live in Wyoming and in August the temps can easily be over 100 degrees F. My issue with the Amsoil product has nothing to do with it's quality but has to do with it being unavailable within 100 miles or more from my home. I don't feel like paying to ship already expensive oil to my home when I can go to walmart and buy mobil 1 off the shelf.

If I switch to Mobil 1 will running the motor until hot allow me to drain off enough of the Amsoil to avoid any real problems (ie the mixing of the synthetics)?

One last question (which I know is an unanswerable question as I've read the battles before)..........Does 10w40 in the cooler months and 15w-50, 5w-50 or maybe 20w-50 in the peak of summer sound like a good plan? The motor's mods as far as I know include just a slightly lumpier cam and an aluminum intake.
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panteradougpanteradougMember
Just drain the old oil out of the pan. Let it drain a couple of days.
I doubt you are going to have any problems changing brands. The amount left in the car is insignificant.

Changing the weights is controversial. The 20w-50 was the recommendation for the Boss 351 from Ford. Don't forget it was natural oil at that point.

I think all you need to run is Mobil 1 10w-40. These engines were designed to run on strait 30 weight.

The changes you see in recommendations are for simplification for production/waranty reasons.

Full synthetic is so superior in wear and breakdown characteristics to natural oils, I don't even think the old terms apply anymore.

Like I said, this is controversial and others probably will disagree.

I will tell you I have been running Mobil 1 in all of my cars since about 1978. It really makes natural oils obsolete.
joulesjoules"Racing is Life, anything before or after is just waiting" - Steve McQueen
Before you switch check the current P & Zn levels of Mobil 1. Typically now only the racing oils have the higher amounts recommended for our older flat tappet cams.

Amsoil is full synthetic and they have a formula that has high Zn & P. Also check into shipping as Amsoil direct shipping is pretty cheap , I pay $9 a case shipping. If you join their preferred member club for $20/yr you also get reduced pricing.

Julian
italforditalfordMember
I use the Comp Cams break in additive in all my cars. The added ZDDP is not supposed to be required for roller cam cars but I play it safe and use it for all the old cars. In your case since you are most likely running a flat tappet cam I would always add ZDDP unless you buy a racing oil. Right now I am using 10W-40 Rotela Diesel oil with the Comp Cams additive.
dave2811dave2811Member
quote:
Originally posted by Clockwork:
....
One last question (which I know is an unanswerable question as I've read the battles before)..........Does 10w40 in the cooler months and 15w-50, 5w-50 or maybe 20w-50 in the peak of summer sound like a good plan? The motor's mods as far as I know include just a slightly lumpier cam and an aluminum intake.


This is answerable when you decode the viscosity grade numbers. Remember that the first number (with the W) is the cold temperature performance, and the second number is the operating temperature performance.

Say it to yourself like this: 10W-40 "behaves like" a straight SAE grade 10 at low temperature, and a straight SAE 40 at operating temperature. That is where the term "multigrade" comes into play. It behaves like two different SAE oil grades across a broad temperature range. In tribology lingo, the multigrade oils have a higher viscosity index than straight grades.

If you had a California car, where the cold start temperature rarely would be below 32*F, then a 20W-50 would be sufficient. I'm a big fan of film strength especially on flat tappet cams so 50 would be the operating temperature regardless. If you really want the best of both worlds for cold starts in the Wyoming winter, then 5W-50 would be the kind, with one caveat. Really broad temperature range performance like that usually use viscosity improvers that can shear down over time reducing the 50 rating, so more frequent changes might be in order. I have a feeling specialty car owners change oil much more often than necessary anyway.
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