Author Topic: gasoline octane rating and leaded/unleaded  (Read 186 times)

bharr

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gasoline octane rating and leaded/unleaded
« on: May 13, 2019, 04:34:28 PM »
The data plate recommends a 72 octane rating for M3 halftracks.  Current fuel is 89 or above.  Will this harm the older engines?  Similarly, unleaded ethanol free is 93 or above and the only leaded gasoline I can find is 110 octane.  Will this hurt the engine?  Is leaded gasoline needed for lubrication and should I be using additives in the unleaded fuel? Thanks in advance for your ides and input.

spillmk1

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Re: gasoline octane rating and leaded/unleaded
« Reply #1 on: May 14, 2019, 04:52:42 AM »
I'm sure there are many thoughts on this subject....

In my experience on low RPM/lightly loaded engines the lack of lead is not a big deal.
But you can always use a lead substitute.
A small price to pay for one less thing to worry about.

As for octane...a higher # won't hurt anything.
Just not needed for our low compression engines.

Ethanol free is DEFINATELY the way to go....would also recommend it in all your lawn equipment.
Much less hassle with gummed up carbs.

My two cents.

Thanks,
Keith
1955 M38A1
1952 M100
1941 M2A1
MVPA Member

bharr

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Re: gasoline octane rating and leaded/unleaded
« Reply #2 on: May 14, 2019, 03:07:43 PM »
Thanks, I knew about the ethanol, just had concern about the octane and lead lubrication issues.

spec4don

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Re: gasoline octane rating and leaded/unleaded
« Reply #3 on: May 14, 2019, 07:10:42 PM »
A lot of folks I know run Aviation Gas. It doesn’t go stale like automotive gas.

Don G.
1941 M2A1 not restored
1942 M3 Diamond T Mostly restored
1943 M3A1 Under restoration
1967 M51A2 Tractor
1945 WC 63 needs restoration
1967 M36 Long wheel base duece
1951 M135 GMC Fire truck conversion

8683jb

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Re: gasoline octane rating and leaded/unleaded
« Reply #4 on: May 14, 2019, 07:33:25 PM »
During the gas rationing of the early- to mid-70's with the even and odd days and all the lines, I could drive right up to the ramp at the local airport, lift the phone and tell them to turn on the 100 octane pump. Fill 'er up and then drive to the FBO and pay them. This was before fences and gates at all airports (thank a muslim for those). That old pickup would run down the road like a striped-assed ape! I'm sure a half track would love it too. As Don said, it doesn't go stale and as a side benefit, there's no better solvent than 100LL!
« Last Edit: May 14, 2019, 11:16:38 PM by 8683jb »
'42 Autocar M2A1

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bharr

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Re: gasoline octane rating and leaded/unleaded
« Reply #5 on: May 14, 2019, 07:38:27 PM »
Yeah, I did a similar thing at our local airport with my 68 Camaro.  Man, that comment brought back some old memories!!!!! Thanks.

R.E.Co.

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Re: gasoline octane rating and leaded/unleaded
« Reply #6 on: May 15, 2019, 08:07:11 PM »
In our old tractors and trucks we always run regular gas with either some 2 cycle oil or diesel fuel added to provide the lubrication for the valves.  The seats in engines prior to the 70's were soft and needed the lead to keep noise and wear down.  Once they went to hardened seats, it didn't matter.  The octane shouldn't be as big of a deal.  Like in a car, you can go up, you just cant go down.  Cant burn regular in a premium engine if that makes sense.  Not sure if this was a help but I got my daily rant in!

Jon
1941 White M2 Halftrack

bharr

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Re: gasoline octane rating and leaded/unleaded
« Reply #7 on: May 16, 2019, 06:29:09 AM »
Thanks for the input. More knowledge is always better.