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Multi weight engine oil

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Wolfpack Rugby

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Any advantage or concern about running a multi weight oil in a 1986 270hp crusader motor ? Just completed top end rebuild. Heads, distributors, manifolds and risers. 1200 hrs. Currently running a 40w.
if multi weight is better, what should I run ?
Lou R.
36 Mainship D/C
 
Multi weight oil is a miracle of chemistry and one of the greatest advances in engine lubrication. So, why beat HELL out of the oil pump gears when trying to pump cold. molasses-like oil when you can have a multi weight that's nice and thin until the motor needs it otherwise?


I know that some stick-in-the-mud old fogies at Crusader continued to recommend old fashion single weight oils for decades, but ask yourself this: What auto manufacturer on earth still specifies a single weight oil? (Answer: NONE.)

Jeff
 
10W30 in the winter, and 10W40 in the summer IF you have oil pressure problems. Otherwise, stick with the 10W30 year round.

Your oil pump gearing will love you for it!

Jeff
 
fastjeff said:
10W30 in the winter, and 10W40 in the summer IF you have oil pressure problems. Otherwise, stick with the 10W30 year round.

Your oil pump gearing will love you for it!

Jeff
Click to expand...

ditto; and just to be clear "oil pressure problems" in this context would be when you come off of a hard cruise run (hot oil), then reduce power to near idle (like when docking), that the low oil pressure alarm goes off. This tends to mean that the viscosity is getting too low when the oil is hot, given your engine clearances. That's a flag to raise the SAE rating from 30 to 40. But, like Jeff says, start with 30 and see how it goes. If using a synthetic (good idea) find a high spread (like 5W-30 or even 0W-30) if available. This helps at cold start-up.
 
fastjeff said:
10W30 in the winter, and 10W40 in the summer IF you have oil pressure problems. Otherwise, stick with the 10W30 year round.

Your oil pump gearing will love you for it!

Jeff
Click to expand...

I use 10W30 all year round as well. Changed every Fall and then put on the 'hard' all winter. (twin 1991 350,s)
 
I used to run straight 30 wt in my 1991 3.0 cause that's what merc said to run, hot oil pressure I thought was a tad low at or near WOT (no I'm not kind to this engine).

Started running 25-40 marine oils or 20-50 Walmart (super tech $12/gal) keeps the pressure up higher (50-60 psi) when I have a boat /tube full of people and the ski prop on. 10 psi per 1000 rpm when hot is a good rule to keep the engine together.

Im sure folks will tell me I'm nuts but this little 3.0 will be at 4200-4800 rpm for an hour straight tubing with the kids, and keeps on ticking...
 
That's amazing little motor has been around for decades! Hard to believe they began in the original Chevy II, made from a straight six with two holes lopped off.

Jeff
 
Well I had 1988 Crusaders, and that's what the manual will suggest a straight 40W or 30W, I ran the 40w after putting in new long blocks and it ran all season here in NY with great 60-70psi oil pressure. You might say I'm old school but was never a great believer of multi viscosity oils. In research something of the same issue, everything I read strongly suggested using an oil that has zinc in it or add a zinc additive to your oil. To my knowledge other than expensive racing oils, Shell Rotella is the only affordable oil on the market today with zinc in it. Tractor Supply on sale will have it for about $3.00 a quart. It comes in 40W, 30W, 10W30 and 15W40. A fellow boater in our marina uses Rotella 15W40 in everything he owns. Another factor to remember is to always change your oil at regular intervals and always before you put it up for the season. Another issue may be that you will see lower oil pressures if you switch from straight weight oil to multi viscosity oil. Hope this helps. Mike
 
Here's the deal; If your motors have flat tappets, then you need the ZDDP additive that modern oils lack. (You can add Lucas ZDDP additive--about 4 bucks--using a half quart per engine.) If your motors have roller tappets, however (as ALL modern engines now have), then the ZDDP is not needed. It was remove to improve emissions.

That said, I also used the Rotella exclusively on my old Chrysler 360s, along with the Lucas additive. And I heartily concur that multi vis oil is the only way to go.

Jeff
 
Down in florida I ran straight 40 and things went OK But, I was doing much of so-called "cold starts" at 90 degree oil temperature. In NY, not so. Agree with the zinc additive, I used ZDDP, there are others. Not so sure about 70psi pressure, sounds high. 40 is stock. Can't imagine the stress on the little flat blade oil pump rod driving cold oil at start up to 70psi on a gen IV big block. Viscosity modifiers in synthetics now have made straight weight oils near obsolete for motors that start near freezing and then run at 200+ degrees. I'm not a synthetic zealot; my highest mileage on a car motor without even a top end job is 350k miles, all on 20W-50 castrol dino oil.
 
Quick recap... It's safe to convert from a single weight ( 30w) to a multi weight ( 10 / 40 ) oil in an older ( 1986 ) gas engine. With all the money I just dropped into these blocks, I want to do what's best. For 30 yrs these engines have enjoyed a single weight oil.

heading out today to buy what this great group will recomend.

Lou R.
36 Mainship D/C
 
You never said what your cold and hot idle and WOT oil pressures were...

I think you cant go wrong with 15-40 Rotella or Pennzoil Marine (same weights). You can also use the Mercruiser or other marine 25-40 which is like $10 more a gal .

Since you only redid the top end I assume the bottom end is a little seasoned in- the thicker oil will probably help. Probably the Rotella is the best value out of those mentioned above. Just make sure you change it at the recommended intervals (50 or 100 hrs?) for me its once a year...

10 psi per 1000 rpm you are running at hot temps and the engine will last a long time...I only went to 40 when I had 40-42 psi at 4800 rpm- boat was always this way on 30 wt, 40 wt got me over 50 psi at that rpm and cold idle around 25 psi. If you're in that area you'll be fine no need to over think it.
 
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