GT40 oil viscosity

[gundog]

1997 SN GT40. 640 hours.
To get high zinc oil I bought Valvoline 20/50. Manual calls for straight 40W. Is the 20/50 high zinc okay for this motor? straight 40 high zinc is non existent here. NH summers. Is it too thick? Will it rob HP and make the motor work too hard?

[SilentSeven]

I ran 15w-40 Rotella in my 1600 hour GT-40. Temps from upper 30's to 90+. No issues, was happy with the outcomes. Rotella is a high zinc oil.

http://pqiadata.org/Shell_Rotella_T4_15W40_4192017.html

[Neptune442]

Amazon has a case of 6 VR1 40W for $42

[hal2814]

The manual is no longer current. The most recent recommendation can be found in this service bulletin: https://www.planetnautique.com/vb5/f...specifications

I personally use Kirklands 15w40 from Costco. It meets all specifications.

[gundog]

thanks to all you guys for responding. I did not know of the updated bulletin. 15/40 it is.

[CHassmann]

It appears the bulletin is for GM engines. Your 1997 GT40 is a Ford. I use the Valvoline VR1 40W in my '02 GT40.

[Jonny Quest]

15W50 or 20W50 with high ZDDP are just fine in your engine. VR-1 dino or synthetic are great oils. Yes, the manual calls for 40 weight, but also mentions multi-viscosity options. I prefer 15W50 over straight 40 weight for better flowability at start up.

Ford vs Chevy. Democrats vs Republicans. Endless debate…

JQ

[windsurfnut]

You'll get tons of opinions on brands/flavors/viscosities on this topic and most have good merit. The most consistent though is Shell Rotella T4 15W40. High in zinc, readily available and often goes on sale (in my area).

[hal2814]

It appears the bulletin is for GM engines. Your 1997 GT40 is a Ford. I use the Valvoline VR1 40W in my '02 GT40.

The bulletin specifically names the GT40 in the “below” group. That being said I imagine the change was in part due to how hard it is to find straight 40w these days.

[kylant]

i always ran Valvoline VR1 40w. Never an issue. looks like 15w-40 is an accepted spec now.

I always heard that synthetic should never be run in the GT40

[Jonny Quest]

I always heard that synthetic should never be run in the GT40

…then hundreds, if not thousands of GT40 engines should be imploding any minute now…

Originally, there was some fear that synthetic oils (and synthetic additives) might damage certain engine seals that were made before synthetic oils were common. That simply has not proven out. Synthetic oil contains engineered molecules and has a naturally higher viscosity index. Oils are tested to ensure they don’t damage engines. Bottom line is that synthetic oils are typically better than Dino oils…that’s why they cost more.

JQ

[scottb7]

…then hundreds, if not thousands of GT40 engines should be imploding any minute now…


JQ

Yeah, and i think this thread more than proves the point that it is not so much what oil you use, but that you actually have oil in the engine that matters. Perhaps a leap of logic, but maybe one can infer that changing it once in a while is a good idea too.

[kylant]

…then hundreds, if not thousands of GT40 engines should be imploding any minute now…

Originally, there was some fear that synthetic oils (and synthetic additives) might damage certain engine seals that were made before synthetic oils were common. That simply has not proven out. Synthetic oil contains engineered molecules and has a naturally higher viscosity index. Oils are tested to ensure they don’t damage engines. Bottom line is that synthetic oils are typically better than Dino oils…that’s why they cost more.

JQ

all I said was that was what I heard. just relaying info, not saying whether it is right or wrong
something about the "tappets" and not enough zinc in synthetics.... I don't know.

[CHassmann]

I had also heard that PCM said not to use synthetic oil. I don't remember the reasoning; however, I agree with scottb7, regular preventive maintenance is very important.

[MN Ryan]

Those finicky PCMs...you actually need to put oil in them.

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