Oil weight question

I get past 90 regularly down below (Lake Oconee) but I can't imagine justifying the upchange to 40weight for the few 90+degree running days you might get up there. If you're on Rabun call Ben McCracken at Lakemont Marine; he's the most knowledgable guy on old inboards in GA as you'll ever find.

Also BuffaloBFN has a 454 BFN on Lanier not far away, send him a PM and ask what weight he uses.

Gary S wrote: And away we go

+2

TRBenj wrote: Oil technology has changed a lot since 1988, I wouldn't suggest following the oil recommendations in the manual. The multi weight oils are much better now than they used to be- a 15w50 acts like a 15w when cold and a 50w when warm, so you get better start up protection than a straight 50w. Most oils have reduced levels of zinc and phos relative to blends of ~10 years ago, so pick the specific oil carefully. Your flat tappet cam motor needs those additives badly. Mobil1 15w50 and Valvoline VR1 20w50 are two excellent choices.

Agree totally! +1

Valvoline VR-1 20W50 has my vote. That's all I use in the 351.

I don't use synthetics because engine always runs between 155 and 160 F therefor does't break down as fast but more so because boat sits for longer periods at a time and the conventional oil tends to stick to cyl walls etc longer.    

I use valvoline 10-40 with a half quart of Rislone Zinc/ADDP additive.

I was going to ask the same thing.

AAM196 wrote: TRBenj wrote: AAM196 wrote: conventional oil tends to stick to cyl walls etc longer.     Where did you get that info? Off an internet thread... lol I was hoping the little yellow guy thing I put in would have indicated I was just having some internet fun... I did read it on some thread when I was researching boats to buy... maybe somewhere here. I run synthetic in my cars and change oil at 5k miles. I run conventional in my boat because I change every 50 hours and end of season + the fact that I rarely even run boat above 4k RPMS and temp NEVER goes above 160F... I feel that I would just be wasting money on the oil. I asked a PCM mechanic who said "the only oil related engine damage he ever saw was caused by lack of oil not type of oil."

I would have too agree. But on the other side, if you have a hopped up engine then synethics are needed. I just ran straight 40w. No probs ever.

Lucas now makes a marine oil in both conventional and semi synthetic with appropriate levels of ZDDP. Mobil 1 in the 5 qt jug at Wallyworld is still the best deal I've found and they have Motorcraft filters too.

I know you's guys are going to beat me up - but

The "stickiest" of engine oils are straight grade (dyno oils)
up to 5X more than multi grades so for long term storage (weeks)
it offers the best cold start protection.

Straight grade is not much help when my wife "drives" to the mail box though.

                                      Aircraft engine & gearbox
                                  Triboligy (oil)lab cert since 1994

   PS
      Seems Shell Rotella (15/40w diesel) is falling out of favor.
      Tested a wally world gal. today 1025 ppm zinc. that's what I use
      Change the oil BEFORE winter high total acid #s etch the soft
      metals (bearings)

      Total acid in oil is a bi product of combustion (blow by in the oil)

1025 ppm zinc is the number I got when I tested it in our oil lab.

I've seen it 975 - 1100 ppm zinc consistently.

When I built this engine, the oil was changed after 1 hour, 2 hrs. 10 hrs,10 hrs now on 50 hr cycles OR at the end of the season.

I'm going to run it Turkey Day then lay up till March. (at abuot 25 hrs.)

"So the PPM Zince test was on Rotella Brand oil? What PPM Zinc content would you reccomend in a flat tappet engine?"

Shell Rotella Diesel 15/40w is what I use so I bring a little to work
and use it for warm up burns in our Spectrometer.

900 - 1100 ppm zinc is good protection for flat tappit cams.
Though I've seen 1200 + I don't know what too much is.

Some break in oils are 2000+ and thats too much to run all the time.
We see aircraft parts that are silver plated (silver is the best wear metal for break in)

900-1100 is ideal for flat tappet cams. Valve springs keep pressure on the cam and most cams are only surface hardened (maybe .030) if you wear thru the surface the cam gets wiped out.

Since the 90s and roller tappets (much less friction) oil has become much cleaner. Less and less zinc. Now zero zinc is normal.   

Clear as mud huh...

Oil will not degrade over a winter layup. The only concern is moisture condensation.