Oil Level Check

[wake_fun]

The factory sticker on top of my engine says to use 89.

[DanielC]

Retarding the timing from factory specs to run a poorer grade of fuel will affect performance. The GT-40 does this automatically, so overall, the performance may suffer a bit. That could mean fuel economy, top speed, or acceleration.
There are many other things that can cause an engine to have detonation, or knock.
The performance I believe would suffer more on an older engine that you set the timing on, because you are "stuck" with that timing.

[east tx skier]

Thanks, Daniel. That's what I figured. I will stick to putting 89 in my 98 Ski for the extra $2--$3 per fill up that it costs me. If that cost ever becomes an issue, I can just put in a gallon less fuel. :-o

[horkn]

Just because power may be very slightly reduced using 87 versus 89, I would not assume that the engine will be any more or less efficient.

My 4.7 v8 4runner has knock sensor(s) and can be run with 87 with no effect on anything but very slightly less hp. IIRC it is only 5 hp less on 87 versus 91 octane per the yota manual.

The 4.2 v8 in my audi is the same way and has at least 2 (maybe 4 ) knock sensors. It can run whatever octane, and I have seen no difference in mpg in using 91, 89, 90 or 87 octane. Or any combo in between due to switching octane of gas with a different octane existing in the tank. Hp and tq is only very slightly down from each grade of gas, but mpg does not get affected because the timing is adjusted to the rating of the octane. The knock sensor on the gt40 is a rudimentary deign ( an add on versus an originally planned knock sensor system on the 2 examples I have shown), but it works the same way.

On a non GT40 EFI motor, aka a carbed one, it will need to have the timing adjusted lightly not to ping in some cases. Ethanol is added to base fuels to make more octane. My carbed 351w does fine even on 87 (e10) despite having gt40P heads with higher compression than the stock 240 hp heads, and the gt40P's were even decked a little, making them have more CR than stock gtp's.

[AirTool]

If my understanding is correct, an increase of 100 degrees F when checking oil would have it expand by 100 * .00039. For 5 quarts, that would be .2 quarts. (This would seem a pretty typical range if you're checking cold around 60-70 degrees and hot around 160-170 degrees.)

I think you need to add another 100 degrees F to your hot temperature yielding a 0.4 quart growth. We know it is over 200+ or the water wouldn't boil out.

We are splitting hairs here, but "full" cold will put you at 0.4 over after a heavy workout. Now if you've ever checked a marine engine with an enclosed dipstick (for sucking oil out) while running, you see the level in the sump is low. (You can't do this on an auto engine because the dipstick isn't enclosed and the oil is splashing around.)

The concern is that when the oil is HOT and the engine speed is low or the motion of the vehicle is high, that the crank will excessively splash oil 1) creating foam and 2) splashing excessive oil on cylinder walls that will then coke.

My opinion sticks: 1) check the oil cold first and make sure it is in there before starting the engine. At this point it should be no less than a quart low. 2) run the engine until it is hot...and not just until the thermostat opens...the OIL needs to be hot. Kill the engine and wait five minutes.

PS - as mentioned in a later post, transmission fluid expands like crazy. I have prior posts on that subject cautioning not to overfill cold transmissions.

[DanielC]

When I change the oil on my 1997 Ski Nautique, I let it drain overnight. I pull the filter off the next day.
I put about a half quart of oil into the center hole of the new filter. I put 4 quarts of oil into the engine. Before running the engine, the oil is above the full mark.
After running the engine, within about a minute, I check the oil level. It is somewhere between the "Add" and "Full" marks.

My engine has only survived 2308 hours, so far, doing it this way.