lets talk about octane in current year gas

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Zed
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lets talk about octane in current year gas

Unread post by Zed » Thu Aug 15, 2019 7:26 pm

First a quick story. When I was way younger I used to buy/restore/sell VW buses before they got stupid expensive and a running bay camper could be bought for a grand all day. Not knowing any better I went by the sticker on the gas flap "91 RON only" and always put in 91 octane, figuuring thats what that meant. Years later I learned 91 RON is actually 87 octane, and there was a switch in the way octane is measured at some point in the late 70s I think.

The point is i am worried I could be making a similar mistake with the gas I put in the 270 now. I recently spent a lot of money driving cross country and used 93 octane, because the general old guy who talks like he knows wisdom I've heard is that "a Mopar 413 barely runs on 93 octane, pump gas used to have a lot more power back when they were new" and I accepted this as gospel fact.

Halfway through the trip I was forced to put in 91 octane when thats the best the town's 3 gas stations had. The Travco seemed to RUN BETTER and I switched up to 91 for the rest of the trip. Likewise I was forced to run 10% ethanol when every pump in Arkansas had nothing but "10% ethanol added" stickers. I've heard the ethanol sticker only applies to lower octane ratings and not the 91 but I don't know really. The Travco seemed to run just fine on what may have been 10% ethanol gas, I had carb overheating issues the whole trip and maybe the ethanol made that worse but it was happening with non ethanol gas too.

What are peoples real life experiences with running lower octane gas in a 413? Anyone ever filled up with 89 or even 87 octane gas and how did that go for you? I'm asking because the cost difference is like $60-$80 a fill up and thats significant.

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Re: lets talk about octane in current year gas

Unread post by KB2CRK » Thu Aug 15, 2019 7:32 pm

It really depends on the year. I have a 76 with a 440 and I run 87 octane with no issue. The 76 440 only has 8 to 1 compression. Check the compression ratio for the idustrial 413 of that particular year and go from there. .

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Re: lets talk about octane in current year gas

Unread post by Woodsman » Fri Aug 16, 2019 7:06 am

The 413 is 7.5:1 it will run fine on regular. It is a truck engine and was built to run 500,000 miles on the cheapest fuel of the day.

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Re: lets talk about octane in current year gas

Unread post by KB2CRK » Fri Aug 16, 2019 7:41 am

Woodsman wrote:
Fri Aug 16, 2019 7:06 am
The 413 is 7.5:1 it will run fine on regular. It is a truck engine and was built to run 500,000 miles on the cheapest fuel of the day.
Theres the answer. I get 8 mpg running 87 Octane pulling a Dodge Journey on a dolly. at 7.5 to 1 compression the 413 would be very happy on the 87 octane.

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Re: lets talk about octane in current year gas

Unread post by Woodsman » Fri Aug 16, 2019 8:15 am

KB2CRK wrote:
Fri Aug 16, 2019 7:41 am
Woodsman wrote:
Fri Aug 16, 2019 7:06 am
The 413 is 7.5:1 it will run fine on regular. It is a truck engine and was built to run 500,000 miles on the cheapest fuel of the day.
Theres the answer. I get 8 mpg running 87 Octane pulling a Dodge Journey on a dolly. at 7.5 to 1 compression the 413 would be very happy on the 87 octane.
8mpg sounds quite respectable when you are what, 40 feet in length, 8 axles and 8 tons?

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Re: lets talk about octane in current year gas

Unread post by KB2CRK » Fri Aug 16, 2019 8:32 am

Woodsman wrote:
Fri Aug 16, 2019 8:15 am
KB2CRK wrote:
Fri Aug 16, 2019 7:41 am
Woodsman wrote:
Fri Aug 16, 2019 7:06 am
The 413 is 7.5:1 it will run fine on regular. It is a truck engine and was built to run 500,000 miles on the cheapest fuel of the day.
Theres the answer. I get 8 mpg running 87 Octane pulling a Dodge Journey on a dolly. at 7.5 to 1 compression the 413 would be very happy on the 87 octane.
8mpg sounds quite respectable when you are what, 40 feet in length, 8 axles and 8 tons?
The 76 Mahal has a GVW of 14500 so Nessie is normally 7 tons all by herself. Add the 4000 lbs of the Journey and 500 lbs for the dolly and it is a bit over 9 tons. She has been to Ohio and Michigan in that configuration. 8 mpg is a true number and she gets that pulling the toad or unladen. She got the same mileage on one trip to Edisto Beach SC pulling my 86 D150 on a dolly.

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Re: lets talk about octane in current year gas

Unread post by raydsimmons » Fri Aug 16, 2019 11:19 am

after 20 plus yrs running my '70 413 on 87 octane I still get close to 10 mpg if I can keep it under 65mph (which is hard to do when it likes 70). had to put 86 octane once out west at it did make a difference with that.

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Re: lets talk about octane in current year gas

Unread post by Zed » Sat Aug 17, 2019 1:08 pm

Ugg sounds like I made the "octane in vintage vehicles" mistake AGAIN and wasted hundreds of dollars on the latest trip. Oh well I should have asked here first, thanks.

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Re: lets talk about octane in current year gas

Unread post by Zed » Sat Aug 17, 2019 1:16 pm

I've got to figure out what the problem is if I ever take this Travco on another trip. I'm starting to think something is messed up with the timing chain, and the previous owner was a idiot who made a lot of dumb Macguver hacks that I've had to fix.

How do you turn over the engine by hand to set the point gap? Thats something I could never figure out so I just left it where it was.

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Re: lets talk about octane in current year gas

Unread post by Woodsman » Sat Aug 17, 2019 1:58 pm

Long breaker bar with a socket on the pulley at the end of the crank.

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