Oil Level Check

[ricofrancois]

Hi I have a 97 GT40 EFI and was wondering if I should check the oil level when engine is cold or warm?

Also what do you guys would fill the gas tank with? (87, 89 or 91 only)

Thanks

[east tx skier]

Warm and 89 Octane.

[AirTool]

Warm and 89 Octane.

Agree on warm....and not just the water temp. It needs a pretty good running to get the oil temp up. Then shut the engine off and let it sit for 5 minutes to let most of the oil report back to the pan.

If cold and in the water (before you start) and you show less than a quart low, you should add a little at a time to get to the quart low line. Note it takes a while for cold fresh oil to fully drain to the pan.

[xrichard]

Why warm?

[AirTool]

Why warm?

The volume of oil expands with temperature. The oil sump volume is based on when the engine is running and the oil is hot. (although the level needs to be checked with the engine off.)

[DanielC]

i agree with the above. Ideally, check the oil with the boat floating, and level in the water,
I recommend using Valvoline VR-1 racing oil, 40 weight. Use a Motorcraft FL1-A oil filter.

[xrichard]

So I got interested in this warm v. cold deal. From various sources using Google, I found the coefficient of expansion of motor oil = .00039 per degree F (...I found a number of different CEs, but they were all pretty close and .00039 came up several places...another way of approaching it is approximately 1% expansion per 1 degree C).

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.)

At the end of the day, being high or low .2 quarts is meaningless. I think consistency is key: when you change, check your oil. Continue to check it at a similar temperature so you know if you've burned oil.

For oil filters, I take advice from this page:
http://people.msoe.edu/~yoderw/oilfi...lterstudy.html

For oil, any oil that meets PCM's spec. Same with gas...whatever meets the spec will work fine. Anything more expensive is likely not getting you any benefit.

[xrichard]

whoops...I meant to type 1% expansion per 14 degrees C

[ricofrancois]

Gas Octane

Thanks for that guys!

Regarding the fuel octane I always fed my GT40 EFI with 87 but was told I should use 91. Someone said 89 is fine. Any more views?

By the way when did 91 came out in the US?

[MARK-S]

89/91

Higher octane may not mean better gas. Go with 87 if you can. If engine has a knock, move up to 89. I thought I had heard that some gas makers use ethonal to boost octane.

[IMPACT-EV1]

The volume of oil expands with temperature. The oil sump volume is based on when the engine is running and the oil is hot. (although the level needs to be checked with the engine off.)

just crazy people it's not tranny fluid it's oil, the amount of expansion is minimal so there is no need to check it while it's hot, have the engine level and pull the dip stick and read it, there isn't a need to clean it and re-insert when the engine is cold and the oil is all ready settled and there will be an easy to read line of oil on the dipstick verse if you do it hot you all ways will have a trail and it can be harder to read the actually level.

Two big advantages of checking oil when the engine is cold and sat for extend period, one you don't need a towel to clean the dipstick first, secondly the line of oil on the dipstick is much more pronounced/defined and visible and easier to read.

[DanielC]

The GT-40 has a knock sensor. You will never hear it knock, unless it malfunctions. The GT-40 can run 87 octane, it was designed that way because there are places where the gas choice is not available.

91 octane gas has been available in Oregon for many years, A lot gas stations only sell two grades, 87, and 91. A few have the third mid grade choice.

[ricofrancois]

Thanks for the replies. I was wondering if 91 was available in California in 97 when the boat was new or even when the engine was designed.

[DanielC]

As near as I can recall, 91 octane has been available ever since the last company to sell leaded 92 octane was Union 76.

Yea, I remember good leaded 92 octane gasoline. For 35 cents a gallon.

[east tx skier]

According to the owner's manual, 89 is recommended, but 87 can be used if 89 is not available provided that timing is adjusted to account for the lower octane fuel. On the MPI GT-40, timing is automatically adjusted to prevent predetonation. So yes, you can run 87 octane, but the timing will be retarded assuming predetonation is imminent.

My question is, does performance suffer as a result of running 87 octane when the timing is adjusted to account for this? Even assuming that performance only theoretically suffers since we don't ever hear a knock since the engine's timing has been adjusted to prevent, does fuel economy suffer as a result of the retarded timing?

If that's the case, and 89 is available, shouldn't we just use 89 at the $2--$3 more per fill up that it costs us?