Oil

[95Ski]

I have a '95 carbureted Nautique that recommends straight 40 weight oil. I have been using Mobil1 Synthetec 5W-50 to cover the 40 weight range. Has anyone had problems with either the straight 40 weight or any synthetics?

[Edwin]

No problems over the years using what the manufacturer recommends. Wouldn't change a thing...

[Tim-Krasin]

Dealer has been doing the oil changes (included in purchase for 3 years), but I'm about to do my first. Dealer's been using straight 40 wt. and I'm considering going to Mobil1 Synthetic. Anyone had specific problems with this synthitic or synthetics in general? GT-40 engine
-Tim

[Flux]

I just talked to a Natique dealer asking what oil to use, they said 20W-50 for the GT-40 (1992). He also told me the filter was a "51515".

Any thoughts?

PS. How many Qts does the Gt-40 Take. My Ford Truck has a 351, and that is about 5.5 Qts.

[JJ]

Oil

I spoke to PCM a couple of years ago. They recommend using straight 40 weight oil in the GT-40. They did not recommend synthetic oil, because some owners like to extend the oil drain periods. They told me that as long as you change your oil often, I change every 25hrs, PCM recommends every 50, that they recommend non-synthetic, heavy duty oil. Penzoil now makes a marine grade with a special additive package just for the high loads of marine engines available in straight 40 weight for Fords, or for the Vortec engines, 15-40.

If you want to give your engine the best protection you can, change it more often than the manual says. The reason oil should be changed is because fuel gets into the oil and delutes it. You usually don't have a dirt problem with marine engines. Synthetics protect well, but they also will be deluted by the fuel. It's my understanding that some synthetics do not mix well with other oils or fuels, but I do not know which brands.

my.02

[wake_fun]

JJ,
How does gas get into the oil unless your guides are bad or your piston rings are shot?
Thanks.

[wake_fun]

JJ,
I've got a 1995 Super Sport with the GT-40 310HP. So I should be using straight 40 weight? Should I use that Pennzoil that you are talking about?
Thanks.

[JJ]

Wake-fun,
a small amount of gas will get past your rings, even when they are in great shape. It happens during the compression stroke. Your engine will also use oil, some more then others. It is normal. Most engines will use no more them 1/4 to 1/2 of quart inbetween changes, some will use up to a quart and still be considered acceptable oil consumption by Ford and Chevy.

Pennzoil Marine is what I currently use. I don't know of any other brands that have a special marine additive packages yet,... except Mercruiser, no thanks. As long as you use good heavy duty straight 40 weight oil from any well known brand and change it often, you will be protecting your engine as good as you can. Most anal-retentive boat owners, myself included , change their oil every 25-30 hours. Cheep insurance for a great investment. I believe PCM recommends 40 weight for all of their Ford 5.8 engines.

[M3Fan]

I hope the 351 is not a 5.8 because I put straight 30 in my 1990.

[Onthewater]

I hope the 351 is not a 5.8 because I put straight 30 in my 1990.

:shock: It sure is a 5.8

[M3Fan]

I'm 99% sure my manual from 90 says 30wt. I'll double check.

[Blue Ski]

I received the following from PCM when asking about straight 40 weight and the synthetic I use:

"PCM recommends 40 weight oil if you are operating your engine above 50
degrees Fahrenheit, 30 weight oil if operating below 50 degrees Fahrenheit.

PCM does recommend synthetic oils. Synthetic oils may offer advantages in
cold temperature pumpability and high temp oxidation-resistance. However,
synthetic oils have not proven to provide operational or economic benefits
over conventional petroleum based oils in PCM engines. Their use does not
permit the extension of oil change intervals.
Hope this information is helpful!!"

[tlb]

Blue Ski, what kind of synthetic do you use. I have always used synthetics in all of my vehicles. I used synthetics in the last two mastercraft boats I owned. Indmar recommends it after 100 hours. These are both chevy engines, PCM and Indmar, Yet my owners manual for my excalibur engine says do not use synthetic oil, dosen't make sense does it? I was planning on using mobil 1 15-50 after 75 or 100 hours.

[NCH2oSki]

PCM doesnt recomend extended change intervals is why they discourage the use of Synthetics. IF you change at the normal times then synthetics will be fine.

[Mikeski]

40w SG rated

As important as the weight is the rating. PCM recommends "SG" or better rating. The SG oil is not designed for engines with catalytic converters so it is a little harder to find. I would use DELO 400 straight 40w, or any other 40w SG oil.
Mikeski