15-40 Rotella versus Straight 40

[David K.]

Hello to all; I'm running a 67-390 hp with standard bore. It currently has straight 40, and I m used to running all my cars on Rotella 15-40. Question,,,, is the straight 40 too thick for this application? Thank you in advance.

[Larry M.]

Re: 15-40 Rotella versus Straight 40

In my opinion YES it is too heavy.

Back in the day when we ran straight weight oil it generally was 20W-20 for most of the year, with perhaps 30 weight during summer months. However, many of us back then (self included) did not have the $ to change oil with the season, so 20W-20 is what the car generally saw. If it burned oil we could increase the oil weight number or add more STP.

15W-40 starts out cold at 15 weight oil, and then gradually thins down to a 40 weight viscosity around 210 F. It is a pretty ideal weight for the older cars............although some could argue 10W-30 is a bit better.

Larry

[David M.]

Re: 15-40 Rotella versus Straight 40

I second this. Straight 40 is to heavy for a gas engine. Multi viscosity oil is better. 10/40 or 15/40 if your in the desert. I run either weight from Schaeffer or Rotella T.

[Joe L.]

Re: 15-40 Rotella versus Straight 40

Hello to all; I'm running a 67-390 hp with standard bore. It currently has straight 40, and I m used to running all my cars on Rotella 15-40. Question,,,, is the straight 40 too thick for this application? Thank you in advance.

David------


I would not use a single viscosity oil in ANY automotive engine, old or new.

[David K.]

Re: 15-40 Rotella versus Straight 40

Thank you gentlemen;

I'm gonna switch over to the 15-40 Rotella, as usual. I ran the car for about 300 miles (nothing crazy with the RPM's).....could I have possibly damaged anything on the motor ? Seals, gaskets, etc....?
Thank you in advance; David

[Paul H.]

Re: 15-40 Rotella versus Straight 40

As long as the ambient temps during those 300 miles weren't too cold, you should be fine. Cold starts (in cold temps) with straight 40 weight oil would not be good for the motor.

[Ronald L.]

Re: 15-40 Rotella versus Straight 40

does not brad penn make an oil specific for our old motors?

[Timothy B.]

Re: 15-40 Rotella versus Straight 40

Thank you gentlemen;

I'm gonna switch over to the 15-40 Rotella, as usual. I ran the car for about 300 miles (nothing crazy with the RPM's).....could I have possibly damaged anything on the motor ? Seals, gaskets, etc....?
Thank you in advance; David

David,

I'm sure you did not hurt anything but It's good to change it out to multi-viz oil like mentioned above.

The only application I can recall that called for straight 40wt oil is a boat engine. I remember being told at the marina the boat engine under power is like a loaded truck going uphill constantly. That was from the sea ray dealer so I'd say they knew a few things about the boats they sell and how to maintain them.

[Ronald L.]

Re: 15-40 Rotella versus Straight 40

Lots of discussion years ago on zinc, anyone have the data?

[Duke W.]

Re: 15-40 Rotella versus Straight 40

Do a web search... Duke Williams corvette engine oil... download and read the article. Nothing has changed other than the new CK-4 API category has replaced CJ-4, and it's "fully backward compatible" with prior C-categories.

Also, the is no need to buy "Rotella". Any 15W-40 rated CJ-4 or CK-4 is best for vintage engines with sliding surface valve trains and they are reasonably priced. Walmart offers the national brands and their own "SuperTech" house brand, which is usually what I buy because it's the least expensive 15W-40 C-category oil.

Duke

[Dick W.]

Re: 15-40 Rotella versus Straight 40

Lots of discussion years ago on zinc, anyone have the data?

You can go to Shells, Valvoline, Delo, etc website and get all the data. Cliff notes, the API classification CF, CH, CJ, and CK oils all have sufficient zinc to satisfy the needs of our engines.

[James W.]

[Duke W.]

Re: 15-40 Rotella versus Straight 40

Like Dick said anyone with a computer and internet connection can search the Web for any oil brand's spec sheet, so if those ninnies can log into Facebook they should be able to find oil spec sheets. The spec sheets usually state the P concentration and sometimes the Zn, but if Zn is not listed you can reasonably assume that it's 100-200 ppm higher than P.

Some of the new CK-4 oils have reduced P and Zn, and it's my understanding that this is because there is less ZDDP than their previous CJ-4, but it's supplemented by a new Boron-based anti-wear additive, however, the spec sheets did not list Boron concentration.

It's also important to understand that the CK-4 test suites are just as rigorous as prior C-categories, which is why CK-4 is "fully backwards compatible" with prior C-category oils.

Duke

[Mark E.]

Re: 15-40 Rotella versus Straight 40

At the risk of reviving another oil discussion, let me share that Mobil 1 offers several products with Zn and P greater than 1,000 PPM. And it's a synthetic designed for "spark" engines. About $23 for 5 quarts at Walmart.

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[Dick W.]

Re: 15-40 Rotella versus Straight 40

At the risk of reviving another oil discussion, let me share that Mobil 1 offers several products with Zn and P greater than 1,000 PPM. And it's a synthetic designed for "spark" engines. About $23 for 5 quarts at Walmart.

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Problem with synthetic oils in older vehicles is that the seals and sealing materials are not "up to snuff" with them. Synthetics will INVENT places to leak. We tried them in our fleet operation years ago, the modern engines designed to use synthetic no problems, the older engines you needed diapers under the engines.