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high octane?
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Peter_Rogers
Jedi Hopeful
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My '69 runs good on 93 octane and I give her a trat of octane boost when she has been a good girl.
tony barnhill
Great Pumpkin - R.I.P
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Chevrom 93 octane does keep the valvetrain clean! I pulled the heads on my 4.3 V6 Sonoma that had almost 200,000 miles & they were almost perfect....& it had more than 97% of the fillups using Chevron 93 octane - back when I bought it new, I signed up in a program with Chevron where, if anything ever went wrong with the fuel part of the engine they'd repair it if 97% of gas was their 93 octane....punched a piston through a cylinder wall...but the valvetrain/heads were perfect when they went on the new engine!
Daimlerdb18
Senior Member
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Here are a couple of links to octane information. The second is more related to LBCs and includes an interesting, if a bit technical, discussion about ethanol blended gasoline.
https://science.howstuffworks.com/gasoline3.htm
https://www.ethanolrfa.org/objects/pdf/DAI960501classic_car.pdf
The comment about race fuel remaining stable is interesting. There is a big "however" to that: not every racing fuel has good long term stability. To be on the safe side an anti-oxidant/gum such as STA-BIL is a very good idea to add to the tank of a car to be put up for the winter.
Also, the additive package that Chevron uses is very good, but, by federal law, all gasolines must contain an effective amount of additives that prevent exhaust valve deposits. High octane gasoline doesn't always equal a sparkly clean head, unless it contains the required additives. Some years ago high octane gasoline got its kick from compounds that could cause valve fouling and carbon deposits in the head, but as EPA regs are tightened those kinds of chemicals are becoming a smaller and smaller part of the mix. So, all modern gasolines must contain additives that assure the engine is clean.
Another interesting tidbit: Gasoline at our favorite gas station probably was not made by the company that's named on the station's signs. East coast gasoline by and large comes from the Gulf Coast and is mixed in the pipeline systems that transport it the 2,000+ miles.
https://science.howstuffworks.com/gasoline3.htm
https://www.ethanolrfa.org/objects/pdf/DAI960501classic_car.pdf
The comment about race fuel remaining stable is interesting. There is a big "however" to that: not every racing fuel has good long term stability. To be on the safe side an anti-oxidant/gum such as STA-BIL is a very good idea to add to the tank of a car to be put up for the winter.
Also, the additive package that Chevron uses is very good, but, by federal law, all gasolines must contain an effective amount of additives that prevent exhaust valve deposits. High octane gasoline doesn't always equal a sparkly clean head, unless it contains the required additives. Some years ago high octane gasoline got its kick from compounds that could cause valve fouling and carbon deposits in the head, but as EPA regs are tightened those kinds of chemicals are becoming a smaller and smaller part of the mix. So, all modern gasolines must contain additives that assure the engine is clean.
Another interesting tidbit: Gasoline at our favorite gas station probably was not made by the company that's named on the station's signs. East coast gasoline by and large comes from the Gulf Coast and is mixed in the pipeline systems that transport it the 2,000+ miles.
tony barnhill
Great Pumpkin - R.I.P
Offline
[ QUOTE ]
East coast gasoline by and large comes from the Gulf Coast and is mixed in the pipeline systems that transport it the 2,000+ miles.
[/ QUOTE ]
True; however, when it arrives out there, the company that buys it out of the pipeline then puts its additives into it, making it peculiar to that brand.
East coast gasoline by and large comes from the Gulf Coast and is mixed in the pipeline systems that transport it the 2,000+ miles.
[/ QUOTE ]
True; however, when it arrives out there, the company that buys it out of the pipeline then puts its additives into it, making it peculiar to that brand.
sultanoswing
Jedi Hopeful
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I run 98 Octane on My 71GT (which is fairly stock I think, although i haven't had the engine apart since I bought the car). At 96 it tends to run-on and pink a little more than on the 98. Wow - I can't believe you guys are running such low numbers - the owner's manual says B's should be run on a minimum of 4 star fuel (which they say is 98 octane). They suggest when running a lower grade to retard the timing a few degrees.
Are the ratings/formulations/blends/additives in the US different from ours in NZ, and those available in the UK when the manuals were printed?
Are the ratings/formulations/blends/additives in the US different from ours in NZ, and those available in the UK when the manuals were printed?
Rob_Edwards
Jedi Hopeful
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[ QUOTE ]
Are the ratings/formulations/blends/additives in the US different from ours in NZ, and those available in the UK when the manuals were printed?
[/ QUOTE ]
Yes. Our fuel is rated as (R+M)/2, or the average or research and motor octanes. As I understand, yours is RON (or research), so the numbers are higher....
Are the ratings/formulations/blends/additives in the US different from ours in NZ, and those available in the UK when the manuals were printed?
[/ QUOTE ]
Yes. Our fuel is rated as (R+M)/2, or the average or research and motor octanes. As I understand, yours is RON (or research), so the numbers are higher....
Offline
[ QUOTE ]
Are the ratings/formulations/blends/additives in the US different from ours in NZ, and those available in the UK when the manuals were printed?
[/ QUOTE ]
A quote from the above reference: https://www.ethanolrfa.org/objects/pdf/DAI960501classic_car.pdf
-------------------------------
"There are two test methods, the Research Method which yields a Research Octane Number (RON) and a Motor Method which yields a Motor Octane Number (MON). The number posted on the gasoline pump is an average of those two numbers, (R+M)/2.
Today, gasoline octanes range for 85 to 94 (R+M)/2 with the typical grades being regular unleaded at 87, midgrade at 89, and premium at 91 to 94. Prior to the eighties, gasoline octane was often posted based solely on the Research Octane Number which allowed postings as high as 100 octane. Premium gasolines sold today often have a research octane number of 100 or higher but must post the (R+M)/2 value. For instance, a 93 octane premium will likely have a motor octane of 85 and a research octane of 101 (101 + 85)/2 = 93.
-------------------------------
USA uses the (R+M)/2 rating system. As it says, prior to the 1980's USA used the "research" rating. Today, many European countries & some others still use the research rating method. Bigger numbers for the same equivalent octane rating. AV gas uses yet another different rating system.
Approximate equivalent ratings:
USA = 87 -- Euro = 91 -- RON = 91 -- MON = 82.5 -- R+M/2 = 87
USA = 89 -- Euro = 95 -- RON = 95 -- MON = 83 ---- R+M/2 = 89
USA = 93 -- Euro = 98 -- RON = 98 -- MON = 88 ---- R+M/2 = 93
USA producers are allowed some variation between their posted pump octane ratings & the actuals. Each batch of fuel may be slightly different & you may find that one brands actual octane ratings variy a bit from day to day. The "must have gotten a bad batch syndrome". In the end, it's a matter of what you are most satisfied with. For most modern cars with adaptive timing controls, few folks will notice much difference between 87 & 93 octane. Older cars excepted, of course.
Additionally, there are seasonal variations in the volatility (how easily the fuel is vaporized) from region to region. This can lead to a more volatile winter blend causing vapor lock on an unusually hot spring day.
D
Are the ratings/formulations/blends/additives in the US different from ours in NZ, and those available in the UK when the manuals were printed?
[/ QUOTE ]
A quote from the above reference: https://www.ethanolrfa.org/objects/pdf/DAI960501classic_car.pdf
-------------------------------
"There are two test methods, the Research Method which yields a Research Octane Number (RON) and a Motor Method which yields a Motor Octane Number (MON). The number posted on the gasoline pump is an average of those two numbers, (R+M)/2.
Today, gasoline octanes range for 85 to 94 (R+M)/2 with the typical grades being regular unleaded at 87, midgrade at 89, and premium at 91 to 94. Prior to the eighties, gasoline octane was often posted based solely on the Research Octane Number which allowed postings as high as 100 octane. Premium gasolines sold today often have a research octane number of 100 or higher but must post the (R+M)/2 value. For instance, a 93 octane premium will likely have a motor octane of 85 and a research octane of 101 (101 + 85)/2 = 93.
-------------------------------
USA uses the (R+M)/2 rating system. As it says, prior to the 1980's USA used the "research" rating. Today, many European countries & some others still use the research rating method. Bigger numbers for the same equivalent octane rating. AV gas uses yet another different rating system.
Approximate equivalent ratings:
USA = 87 -- Euro = 91 -- RON = 91 -- MON = 82.5 -- R+M/2 = 87
USA = 89 -- Euro = 95 -- RON = 95 -- MON = 83 ---- R+M/2 = 89
USA = 93 -- Euro = 98 -- RON = 98 -- MON = 88 ---- R+M/2 = 93
USA producers are allowed some variation between their posted pump octane ratings & the actuals. Each batch of fuel may be slightly different & you may find that one brands actual octane ratings variy a bit from day to day. The "must have gotten a bad batch syndrome". In the end, it's a matter of what you are most satisfied with. For most modern cars with adaptive timing controls, few folks will notice much difference between 87 & 93 octane. Older cars excepted, of course.
Additionally, there are seasonal variations in the volatility (how easily the fuel is vaporized) from region to region. This can lead to a more volatile winter blend causing vapor lock on an unusually hot spring day.
D
tony barnhill
Great Pumpkin - R.I.P
Offline
Good thread!
Daimlerdb18
Senior Member
Offline
The lower octane at higher altitude is certainly true. Cooler air temps do the same thing in general.
The points mentioned in the thread are more germane to our LBCs which have carburettors and no computer control for the ignition, modern cars are made to adjust engine conditions to prevent pre-ignition. My understanding is that gasoline of lower octane that recommended results in lowered fuel economy, but the converse is not really true. Although most premium fuels are denser than regular fuels and should, in general, yield incrementally more mpg. Although I'm sure the cost difference would not justify the mpg gain. It's interesting to see the spread between wholesale prices of regular and premium and then see the really big difference in retail pricing at the pump. There are times when I've seen in the Houston area only two to three cents per gallon wholesale difference and nearly twenty at the pump.
The points mentioned in the thread are more germane to our LBCs which have carburettors and no computer control for the ignition, modern cars are made to adjust engine conditions to prevent pre-ignition. My understanding is that gasoline of lower octane that recommended results in lowered fuel economy, but the converse is not really true. Although most premium fuels are denser than regular fuels and should, in general, yield incrementally more mpg. Although I'm sure the cost difference would not justify the mpg gain. It's interesting to see the spread between wholesale prices of regular and premium and then see the really big difference in retail pricing at the pump. There are times when I've seen in the Houston area only two to three cents per gallon wholesale difference and nearly twenty at the pump.