PCM GT 40 and syn oil

[Gregmacdog]

I am thinking of changing my engine oil, and changing over to full synthetic, does anyone have any experience and recommendations for this.
Brands, types, weights?
Any thoughts, THANKS...

[michael hunter]

Mobil 1 15w50 is the only weight of Mobil 1 that has the correct amount of ZDDP for flat lifter engines.

[Gregmacdog]

Mobil 1 15w50 is the only weight of Mobil 1 that has the correct amount of ZDDP for flat lifter engines.

Thanks for the input. That's what I needed to hear.

[cadunkle]

Zinc and phosphorus levels in any off the shelf oil are not a concern in a stock PCM 351w. The cams used are very mild with low lift and gentle ramp rates that it's a non-issue. Run whatever you prefer, synthetic is generally a better oil and will be fine to run. I would not run a 15w50 oil unless you've built the engine with clearances for that or have an oil pressure or other oiling issue. Keep in mind while we typically use our boats in warmer summer months they do have colder thermostats than most automotive versions of these engines, either 142* or 160* and of course are cooled with an infinite supply of cold water.

Either 30 or 40 weight are what PCM recommends and are typical oils to use in any 351w automotive or marine. Personally I've always used 10w40 in my marine engines and had no oiling issues. I use dino oil, typically Valvoline but will run other oils when on sale. Use a quality filter, not Fram. I use Purolator PL30001 filters on my Ford engines, though will use a L30001 or Motorcraft FL1-A in a pinch. Any Wix filter (commonly rebadged NAPA and others) are good as well.

While zinc and phos levels aren't important with the mild cams in these engines, if you're that worried about it just run whatever oil you like and add a bottle of Comp Cams (or any other) cam breakin additive with each oil change. Higher than required zinc and phos levels won't hurt anything. I would prefer to run a suitable viscosity oil and use an additive over using a thicker oil than required, which may accelerate wear.

[michael hunter]

I agree about the Fram orange filters. Worst filter you can buy. The Mobil 1 or C&N filters are the best. Not sure about your theory about mild cams not needing proper ZDDP levels . Why would 10w40 be a better choice than 15w50? In 89 PCM recommended 10w30 or 20w40 API SE oil the SE classification has been discontinued. Currently Mobile 1 15w50 has an API SN, SM, SL, SJ grade more than sufficient for both older and newer high load engines. In today's roller cam engines ZDDP is not as important so many oils have either lowered or completely left it out. When in doubt I always fall on the side of caution . I called Mobil and got the information to determine what oil is the best choice in my engines. I have been using Mobile 1 in all my cars, boats, Motorcycles and lawn mowers since 1977 . I guess you could say I'm sold on their products. Do your own research and make your own choice.

[supratj]

I have been running Royal Purple 10w30 for 4 years and the engine loves it. After the first two years of changes, the oil stays clean with no usage and no blow by. It seems to have eliminated carbon buildup smoothed out the engine. I also run it in my F350 7.5 farm truck with the same results.

Jay

[SquamInboards]

My only caution would be switching an engine that has been run on conventional oil, over to synthetic. How many hours are on the engine now? I think changing back and forth can cause more issues than using any oil consistently... I'm sure some others will chime in on this.

[michael hunter]

I remember years ago there was talk about synthetic causing oil leaks. I have never found that to be true . I run Mobile 1 in all my engines that includes bikes, cars ,boats and even lawn mowers. I have never had a oil related failure in the last 40 years. Thats not to say Mobile 1 is better than other brands of synthetic oil . I do believe synthetic is much better than conventional oil. No matter what you use the key is to change regularly .

[TitanTn]

I remember years ago there was talk about synthetic causing oil leaks. I have never found that to be true . I run Mobile 1 in all my engines that includes bikes, cars ,boats and even lawn mowers. I have never had a oil related failure in the last 40 years. Thats not to say Mobile 1 is better than other brands of synthetic oil . I do believe synthetic is much better than conventional oil. No matter what you use the key is to change regularly .

I heard that a while ago too, but it was in relation to switching a conventional oil engine over to synthetic. It was described as synthetic having more detergents, or being cleaner in some way and it would clean out deposits that conventional oil couldn't, and if you had tired seals they would leak. Always sounded like a lot of "if" "then" statements.

[chris young]

It took me a while to dig this up, but it's very informative. http://www.bobistheoilguy.com/motor-oil-101/
There's 10 pages of reading there, so you can come to your own conclusions. Two things stuck with me in the article, the first was that you want to run the weight of oil which will result in 10 psi per 1000 RPM. The other was that they are all nearly the same weight when warm, but change considerably when cold. I'm going to re read it before my spring oil change but my conclusion after first reading was light synthetic. And, IIRC they covered ZDDP there as well saying that other additives were being used to replace it, so you need to know what else is in the oil.

BTW, I know that both Michael Hunter and Cadunkle know vastly more about motors than I do, I am not an expert, I just do my research and come to my own conclusions.