Oil type for GT40 98 Ski Nautique (synthetic)

[cragginshred]

I am running synthetic and used amsoil last year. Unsure If I want to use it this year. What are you guy putting in your GT 40 ford engines? Please don't try and talk me out of synthetic, too late.
Don

[bhectus]

Always ran Valvoline VR1 in my Ford engines. But if you want to stay with synthetic, you can't go wrong with Mobil1.

[BrennanK]

I have used VR1 as well. I use 20w-50. I like the VR1 due to the high concentration of ZDDP. That is the additive you want have because of the flat tappet cam in the GT-40. I don't really care what you run, just make sure it has a high level of zinc/phosphorus.

For what I do there is no point to synthetic. My oil change intervals are not long enough to warrant the use of synthetic. If I wanted to run high hour oil change intervals I might consider synthetic. I'm not trying to talk you out of synthetic either, just sharing my thoughts for others...

[Nautiquehunter]

I use Mobil 1 in all my boats [ 2-Supras 351w, 1 210 5.7 and 1 pontoon 3L] . I use the 15w50 it has all the protection the flat tappets need . I still change at 50 hours . I buy the Mobile 1 or K&N filters on line .I find them on eBay motors for 5 dollars or less . I buy 6 at a time since 3 boats use the same filter. You can get Mobile 1 at Wall mart 24 dollars 5 qt jug.

[DanielC]

I have 2485.7 hours on my 1997 Ski Nautique, using Valvoline VR-1 40 weight. I use the Motorcraft FL1-A oil filter.
Last time I bought oil filters, I got them at WalMart, less than $4.00 each.

Modern oils, including synthetics are for modern roller cam engines. The GT-40 is not this type of engine. The higher levels of zinc and phosphorus additives flat tapper engines need is being phased out of most all oils. The Mobile 1 you buy today is not the Mobile 1 you bought five or ten years ago, and it will also change in another five or ten years. Make sure it does have the ingredients your old engine needs, the engine does not change.

[dgcamero]

I have 2485.7 hours on my 1997 Ski Nautique, using Valvoline VR-1 40 weight. I use the Motorcraft FL1-A oil filter.
Last time I bought oil filters, I got them at WalMart, less than $4.00 each.

Modern oils, including synthetics are for modern roller cam engines. The GT-40 is not this type of engine. The higher levels of zinc and phosphorus additives flat tapper engines need is being phased out of most all oils. The Mobile 1 you buy today is not the Mobile 1 you bought five or ten years ago, and it will also change in another five or ten years. Make sure it does have the ingredients your old engine needs, the engine does not change.

We used Rotella 15w40 until we switched to synthetic. We now use an oil that meets the Mercedes 229.5 -AND- BMW LL-01 specifications, in a Ow40 or 0w30 weight with the AutoZone or Advance special oil filter (usually Bosch or Mobil 1) Usually that is Mobil One 0w40 or Castrol 0w40. Have also used Castrol 0w30 (very thick 30), but it is difficult to find lately. The Mercedes and BMW specs require a minimum 900 ppm ZDDP and hold oil pressure much more consistently under heavy hot load than Rotella. Once I switched it to synthetic, I change it every 100 hours or 2 years, whichever comes first. Had the boat since it was new and it just clicked over 1200 hours without a hitch...I have never seen the straight 40 weight the owners manual calls for! Impressive on your hours, DanielC!

[TRBenj]

I have 2485.7 hours on my 1997 Ski Nautique, using Valvoline VR-1 40 weight. I use the Motorcraft FL1-A oil filter.
Last time I bought oil filters, I got them at WalMart, less than $4.00 each.

Modern oils, including synthetics are for modern roller cam engines. The GT-40 is not this type of engine. The higher levels of zinc and phosphorus additives flat tapper engines need is being phased out of most all oils. The Mobile 1 you buy today is not the Mobile 1 you bought five or ten years ago, and it will also change in another five or ten years. Make sure it does have the ingredients your old engine needs, the engine does not change.

Mostly true... but the aforementioned M1 15w50 does in fact have the higher levels of zinc and phos that are needed for flat tappets. That is not true for all M1 oils, however... just the 15w50.

[Marko1956]

I see several oil weights mentioned here. My owner's mannual says to use straight 40 weight, but the tag on the engine (GT 40) says 10-40. I'm in New England and only use the boat in warm weather. Which is the better choice?
PS This is my first year with the Nautique, a 1992. It replaced an American Skier.

[TRBenj]

Ideal weights for us here in NE include 15w40, 15w50 and 20w50. Not all oils with proper ZDDP are made in all weights. Stick with Valvoline VR1 20w50 or Mobil1 15w50 and you'll be fine.

A lot has changed in the world of oils since that PCM manual was written 15 years ago.

[DanielC]

"A lot has changed in the world of oils since that PCM manual was written 15 years ago. "

But the engine in my boat is still the same flat tappet engine it was in 1997. Oils have changed. Mostly to meet stricter requirements from the EPA, and engines have changed to roller cam designs to accommodate the newer oil requirements.

[toddrswenson]

I've always used Royal Purple SAE 40. I know it's expensive, but it meets the specs and my O'Reilly auto parts always has it or can get from the warehouse in a couple of hours. I don't ever put on more than 50 hours a season so a little premium cost for the once a year expense isn't that big a deal.

[TRBenj]

"A lot has changed in the world of oils since that PCM manual was written 15 years ago. "

But the engine in my boat is still the same flat tappet engine it was in 1997. Oils have changed. Mostly to meet stricter requirements from the EPA, and engines have changed to roller cam designs to accommodate the newer oil requirements.

Precisely. Which is why blindly following an outdated manual is a bad idea.