www.iFourWinns.com

I own a few older vehicles and recently got to wondering what the proper oil for my new (old) Chevy 230 hp V8 would be. Most marine engines built before the mid-90's had flat tappet cams, not the roller cams you see in modern engines. To prevent premature cam wear, oils for older engines need to be formulated with ZDDP, a Zinc and Phosphorus additive. Modern oils have reduced amounts of ZDDP because of EPA requirements and potential damage to catalytic converters.

I have long used Shell Rotella T3 15W40 in my elderly vehicles but recently learned it has been discontinued and replaced with Rotella T4. Talking to Shell lubrication engineers I've found that the new oil also offers the protection that my older engine needs. Another approach you can use is to use a ZDDP additive (about $10 per treatment) with your modern oil.

For oil geeks this table shows the specs of some of Shell's current and former oils.

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1987 Sundowner 215
Mercruiser 230/V8 - Alpha One Gen 1
Previous Boat
1973 Starcraft 21' Chieftain 120 HP Mercruiser I/O
PADI Master Diver
IANTD Technical EANx Diver
Commercial Pilot
Flight Instructor

Interesting data and useful for the owners of older vehicles and boats. I have a roller cam in my old '88 4.3. When I took the top end of the engine apart to repair the blown head gaskets, I wound up also replacing the cyl heads at the recommendation of the machine shop I used. I took out each lifter and after 29 years of use, the roller lifters and cam lobes looked like new! In this engine I used to use Chevron Delo 400 straight 30 or 40, then switched to the Mercruiser/Quicksilver 25/40. Based on your data, the Shell oil has more zinc and phosphorus than the Merc oil does based on a oil sample I tested. So for older non-roller cam engines the Shell may well be better.

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

I wonder what kind of cam the Volvo 5.0 GXi has. I’ve been using Sierra SAE 30 and about a quart of synthetic 5W30 for changes.

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2006 Four Winns Horizon 200
Volvo Penta 5.0 GXi/SX

I would think a 2006 engine must have a roller camshaft. The only engine I know of that was never converted over to rollers over its long production run was the Jeep 4.0 inline 6. We still have ours and it’s about to reach 180,000. I’ve been running it on Valvoline Maxlife with good results.

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

I pulled out some old oil analyses I had done with Blackstone Labs on my 4.3.
When I was running the Chevron Delo 400 straight weight it had 1705 ppm of Zinc and 1400 ppm of Phosphorus. With the Merc 25/40 I got 960 ppm of Zinc and 814 of Phosphorus. But the Chevron oil has probably been reformulated because that report is from back in 2011 so I bet the levels are lower now. In any case on this engine it does not really matter due to the roller cam. The Merc 25/50 data is from 2015.

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88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II