Diesel oil in a gasoline engine

Good piece about this topic on MotorTrend's website:

"...the type of ZDDP in a diesel engine oil is not the same as the ZDDP in a gasoline engine oil. This is an important difference; diesel engines run at lower rpm than gasoline engines, so that difference in engine speed changes the way the ZDDP needs to activate to provide anti-wear protection. To get a little technical, diesel engine oils typically contain primary ZDDP and gasoline engine oils contain a blend of secondary and primary ZDDP. Just as a side note, racing oils just contain secondary ZDDP. Both types of ZDDP offer anti-wear protection, but the gasoline type of ZDDP provides more protection for higher-speed engines (think bigger valvesprings)."

Our local Costco had Kirkland Heavy-Duty Diesel 15W-40 oil on sale for $10 per gallon last week. Was tempted to try it - until I read that article.

Ended up using Pennzoil conventional 10W-40 and a ZDDP supplement.
Valvoline VR1 is great, too.

I don't know what the "best" oil is, but I know most of the readers of these forums love their boats. And, until last year, I was totally ignorant about the need for zinc in engines with flat tappet cams.

Hopefully, the MotorTrend article will educate some folks who have older engines and allow them to make better informed decisions. 

I agree with KENO that many engines survive just fine with "non recommended" oil.  Per PCM, the recommended oil for many years was 40 weight.  To my knowledge, I've never yet run straight 40 weight in either of my Ski Nautiques.  I've run Shell Rotella T6 in just about everything from lawn mowers to my new PowerStroke diesel  -- even in my flat tappet 351 SBF on occasion.  

It's an "oil thread" Buck.  Ask 10 people and get 15 responses!

That same curious person might be wondering why the  oil of his favorite brand, which doesn't contain the "magical" amount of zinc hasn't turned his 30 plus year old engine's camshaft into just plain junk. This could be Buck and a whole bunch of other people too 

When is it fashionable/courteous for people to blame every gas related issue they have on ethanol Gary?

63 Skier wrote: Right Gary, but it's always winter somewhere ...

https://www.speedwaymotors.com/the-toolbox/zddp-content-chart-high-zinc-oil-list-brand-breakdown/32479

List of oils with high zddp
Lucas 3000 ppm
Rotella 1500 ppm
Most regular 600

Sorry my link sucks

Thank you Sir
VR1 same as rotella

KENO

Ken,

I assume the oil used in the boat's engine during the critical break-in period and early years of the 1990s had a higher concentration of zinc. Don't know for sure.

And I haven't inspected the cam lobes for signs of excessive wear.

Was merely passing along some info. that I thought might be of interest to members of this forum.

Ken, I'm not following your thinking on this. 

We use Valvoline 20W50 in all our old boats because the info is out there to use zinc and it seems reasonable.  The only reported wiped out cams I've seen reported on CCF were due to breaking in a new cam and not due to using modern oil in an old engine.  I'm still waiting to hear about one of those.  We have a 1988 Malibu Skier that we got with 150 hours and for the next 1000 or so hours it got modern Castrol or Valvoline oil with low zinc and it still is running fine. Same with Fram oil filters, I ran one of those in a 1994 F150 for 14 years and 200K miles as well as in that Malibu Skier and no problems.  I'm either lucky or some info gets overblown.