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Whaanga
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Joined: May 07, 2016
Posts: 625
Location: Rochester, NY
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 Posted: Tue Oct 16, 2018 7:30 pm Post subject: 90 vs 91 Octane Gasoline |
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I have been using 91 Octane non-ethanol gas in my 73 bus. But as of late the gas station has now changed the non-ethanol grade to 90 Octane. Can I still use this or do I need to switch to a higher octane grade that includes ethanol?
Thanks,
Jeff
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kreemoweet
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Joined: March 13, 2008
Posts: 3897
Location: Seattle, WA
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| Posted: Tue Oct 16, 2018 7:38 pm Post subject: Re: 90 vs 91 Octane Gasoline |
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The "regular" grade gas everywhere in the U.S. meets the "90 RON" (Research Octane Number) specified by VW
for all their air-cooled vehicle engines.
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sjbartnik
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Joined: September 01, 2011
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Location: Brooklyn
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| Posted: Tue Oct 16, 2018 8:40 pm Post subject: Re: 90 vs 91 Octane Gasoline |
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Regular being 87 octane by the USA method.
Note the USA method is different than the Euro method, RON. So 91 RON is roughly equivalent to 87 in the USA.
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wihr
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Location: PORTLAND, OR
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| Posted: Tue Oct 16, 2018 10:08 pm Post subject: Re: 90 vs 91 Octane Gasoline |
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I have used "regular" in my Bus for 48 years. It "pinged" early on when hot. I adjusted the timing slightly. No ping for the last 40 years. 91 octane just means more money.
WW
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Wildthings
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Joined: March 13, 2005
Posts: 50332
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| Posted: Tue Oct 16, 2018 10:36 pm Post subject: Re: 90 vs 91 Octane Gasoline |
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| wihr wrote: |
I have used "regular" in my Bus for 48 years. It "pinged" early on when hot. I adjusted the timing slightly. No ping for the last 40 years. 91 octane just means more money.
WW |
I would agree with you that you don't need the extra octane, but getting rid of the ethanol is important at times. I run ethanol free during the hottest months of summer to get easier hot starting and then if I am not going to be using the rig during the winter it will get a fill of ethanol free then as well. Yes it cost me extra to do this, maybe 50 bucks a years, but 50 bucks is way cheaper than a upper end rebuild if gum builds up on the valve stems seizing the valves in their guide so that the pistons slam into them. Don't particularly like annual carb disassembling and jet cleaning either. |
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airschooled
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Joined: April 04, 2012
Posts: 12721
Location: on a bike ride somewhere
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| Posted: Wed Oct 17, 2018 5:51 am Post subject: Re: 90 vs 91 Octane Gasoline |
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| kreemoweet wrote: |
The "regular" grade gas everywhere in the U.S. meets the "90 RON" (Research Octane Number) specified by VW
for all their air-cooled vehicle engines. |
Yes! This is so important.
Saying 91 is like saying our buses are 14 long. 14 what? Feet? Inches? Meters? Measurements need units, and though octane content is a unit, it is not universal around the globe. The Car Talk guys did a nice job simplifying it for us:
https://www.cartalk.com/content/what-formula-gas-pump-all-about
And even though they not the octane rating itself won't help keep your engine clean, the premium additives that individuals plans add to supreme formulas and they like may help. There was a thread here three or four years ago where someone posted actual empirical data(!) regarding additives in high test gas but I can't find it.
Long story short, run what you like. If you have a stock engine you can get by on whatever is cheapest as long as there isn't water in it. Performance builds might need higher octane at the discretion of the builder and your gauges.
Robbie
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Spike0180
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Joined: June 06, 2015
Posts: 2269
Location: Detroit, Michigan
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| Posted: Wed Oct 17, 2018 6:32 am Post subject: Re: 90 vs 91 Octane Gasoline |
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| asiab3 wrote: |
| kreemoweet wrote: |
The "regular" grade gas everywhere in the U.S. meets the "90 RON" (Research Octane Number) specified by VW
for all their air-cooled vehicle engines. |
Yes! This is so important.
Saying 91 is like saying our buses are 14 long. 14 what? Feet? Inches? Meters? Measurements need units, and though octane content is a unit, it is not universal around the globe. The Car Talk guys did a nice job simplifying it for us:
https://www.cartalk.com/content/what-formula-gas-pump-all-about
And even though they not the octane rating itself won't help keep your engine clean, the premium additives that individuals plans add to supreme formulas and they like may help. There was a thread here three or four years ago where someone posted actual empirical data(!) regarding additives in high test gas but I can't find it.
Long story short, run what you like. If you have a stock engine you can get by on whatever is cheapest as long as there isn't water in it. Performance builds might need higher octane at the discretion of the builder and your gauges.
Robbie |
Yup. Just yup.
I for one have to run premium due to my high Compression Ratio (9.25-1), and I had pinging at 30*adv so I also retard my timing to 28.5 (as of now, and that is up .5 from last tune, so far so good.). So it depends on the build, but with a normal CR, normal 87 US RON is just fine.
Though you may want to stick to a set RON and tune appropriately, I know I saw the engine in my 04 Passat (1.8t engine, so might not apply to NA as much) smooth out when I used higher RON, so there must be a slight burn difference. A proper tune should run 87 just fine and maintain similar temps.
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Q-Dog
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Posts: 8699
Location: Sunset, Louisiana
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| Posted: Wed Oct 17, 2018 6:43 am Post subject: Re: 90 vs 91 Octane Gasoline |
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Been running 87 octane with ethanol in all my VWs for 30 years. No issues. Anything else is just wasting money.
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WhirledTraveller
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Joined: January 09, 2008
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Location: Cambridge, MA
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| Posted: Wed Oct 17, 2018 7:58 am Post subject: Re: 90 vs 91 Octane Gasoline |
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| Q-Dog wrote: |
| Been running 87 octane with ethanol in all my VWs for 30 years. No issues. Anything else is just wasting money. |
Please make sure your fuel lines are up to snuff, however. Old fuel lines should be replaced on general principle (whatever happened to the "up in flames" sticky?) , but also because some of the old rubber isn't compatible with ethanol. Refer to the fuel lines thread https://www.thesamba.com/vw/forum/viewtopic.php?t=474405
Also the OP is running a 914 engine in a bus. Depending upon the exact build, running a higher octane fuel is potentially a reasonable precaution as some 914 engines ran higher compression numbers and called for a higher RON.
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SGKent 
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Joined: October 30, 2007
Posts: 41031
Location: Citrus Heights CA (Near Sacramento)
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| Posted: Wed Oct 17, 2018 9:54 am Post subject: Re: 90 vs 91 Octane Gasoline |
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| Whaanga wrote: |
I have been using 91 Octane non-ethanol gas in my 73 bus. But as of late the gas station has now changed the non-ethanol grade to 90 Octane. Can I still use this or do I need to switch to a higher octane grade that includes ethanol?
Thanks,
Jeff |
be sure you read the pump label correctly. There are several different ways of posting Octane ratings. They are not equal and the difference can be substantial. Is it 90 Octane AKI, 90 Octane RON, or 90 Octane MON? Is it 90 Octane MIN one of the qualifiers above? Also what elevations are you driving around at? Someone at sea level has a different environment than someone at 6,000 feet all the time. Generally a 1 Octane difference in the same measuring system is not all that big of a change. It could be the result of testing, the kind of testing, state laws, or a change in refineries - which one might benefit or lose in that change. Here in Sacramento the gasoline is pumped thru pipelines to tanks in this area. The trucks pick up the baseline product, blend in the additives to a formula and deliver it to the stations. I believe that there are two different baseline blends here that get combined with additives for the final Octane AKI.
See https://en.wikipedia.org/wiki/U.S._State_Fuel_Octane_Standards for standards in the US.
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telford dorr
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Location: San Diego (Encinitas)
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| Posted: Wed Oct 17, 2018 11:03 am Post subject: Re: 90 vs 91 Octane Gasoline |
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Another side note: as far as I know, the oil companies only sell two types of gas: 87 and 91 octane. The 89 middle pump merely mixes the two together (actual ratio is anybody's guess). In short, don't buy middle pump - mix the two yourself if you really need something more than 87.
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Wildthings
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Joined: March 13, 2005
Posts: 50332
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| Posted: Wed Oct 17, 2018 12:12 pm Post subject: Re: 90 vs 91 Octane Gasoline |
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| telford dorr wrote: |
| Another side note: as far as I know, the oil companies only sell two types of gas: 87 and 91 octane. The 89 middle pump merely mixes the two together (actual ratio is anybody's guess). In short, don't buy middle pump - mix the two yourself if you really need something more than 87. |
I agree it all runs through the same pipes, along with Diesel. They just have a sequence they use to keep each fuel reasonably pure when they go from pumping one fuel to another. |
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Abscate
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| Posted: Wed Oct 17, 2018 1:00 pm Post subject: Re: 90 vs 91 Octane Gasoline |
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You can buy 93 and 97 where I am. Those could just be blends of the ends, of course.
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Q-Dog
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Posts: 8699
Location: Sunset, Louisiana
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| Posted: Wed Oct 17, 2018 5:21 pm Post subject: Re: 90 vs 91 Octane Gasoline |
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| WhirledTraveller wrote: |
| Q-Dog wrote: |
| Been running 87 octane with ethanol in all my VWs for 30 years. No issues. Anything else is just wasting money. |
Please make sure your fuel lines are up to snuff, however. Old fuel lines should be replaced on general principle (whatever happened to the "up in flames" sticky?) , but also because some of the old rubber isn't compatible with ethanol. Refer to the fuel lines thread https://www.thesamba.com/vw/forum/viewtopic.php?t=474405
Also the OP is running a 914 engine in a bus. Depending upon the exact build, running a higher octane fuel is potentially a reasonable precaution as some 914 engines ran higher compression numbers and called for a higher RON. |
All of my VWs get new fuel lines every 2-3 years. I've been doing that since before ethanol was added to our fuel.
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Whaanga
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Posts: 625
Location: Rochester, NY
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| Posted: Wed Oct 17, 2018 7:46 pm Post subject: Re: 90 vs 91 Octane Gasoline |
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Thanks for all the great comments here. Much appreciated. I replaced my fuel lines two years ago. I've driven the bus about 2,500 miles since - What is the criteria for replacement? Time? Mileage? Other factors?
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Abscate
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| Posted: Wed Oct 17, 2018 7:58 pm Post subject: Re: 90 vs 91 Octane Gasoline |
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Failing your quarterly inspection or reaching the 5 year mark.
On boats, you actually blow your bilge every time you use the engine...a fan pushes air over the engine and you sniff for fuel.
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raygreenwood
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Joined: November 24, 2008
Posts: 21507
Location: Oklahoma City
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| Posted: Wed Oct 17, 2018 9:29 pm Post subject: Re: 90 vs 91 Octane Gasoline |
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| telford dorr wrote: |
| Another side note: as far as I know, the oil companies only sell two types of gas: 87 and 91 octane. The 89 middle pump merely mixes the two together (actual ratio is anybody's guess). In short, don't buy middle pump - mix the two yourself if you really need something more than 87. |
No. Actually there are certified grades of gasoline with and without ethanol using the standard North America octane number calculations...all the way up to 94 octane...and higher in limited markets.
These are not specialty racing fuels. These are pump gas. Ray |
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Wildthings
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| Posted: Thu Oct 18, 2018 12:20 am Post subject: Re: 90 vs 91 Octane Gasoline |
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| Whaanga wrote: |
| Thanks for all the great comments here. Much appreciated. I replaced my fuel lines two years ago. I've driven the bus about 2,500 miles since - What is the criteria for replacement? Time? Mileage? Other factors? |
Never heard of any criteria, as on modern cars the factory supplied FI hose tends to last the life of the vehicle. I would say that changing out a 30r9 rated hose every ten years should be fine, but with the ongoing changes in the fuel who could know? |
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raygreenwood
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Location: Oklahoma City
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| Posted: Thu Oct 18, 2018 6:40 am Post subject: Re: 90 vs 91 Octane Gasoline |
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In modern cars.....about 90% of all fuel line is a combination of steel and nylon. The inly places tbey run rubber lines is flex joints before and after the fuel rail. And they are all swaged couplings and premium line. Yep about 10 years.
Ray |
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WildIdea
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Location: Black Hills, South Dakota
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| Posted: Thu Oct 18, 2018 7:23 am Post subject: Re: 90 vs 91 Octane Gasoline |
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It’s hard for me to tell a difference on 87-91 in my modern vehicles. Would the computers in newer vehicles sense the difference and make adjustments? Sometimes I get better mileage out if 91 in my f-150.
I do think that on my smaller engines like my mower, weed eater or power washer, gas can etc, that 91 will store better or longer setting around for extended periods. I would still use a stabilizer for something setting over a winter. When I pulled my tank out of my Westy, it had been sitting 20 years, the tank of gas had settled into a molasses crude at the bottom of the tank and a thinner clearer liquid at the top. Percolated from gravity to basically pre refinery crude I guess, who knew.
Also, on my motorcycle, with its tank just sitting out in the sun baking would be a harsh environment for gas and would think that could change the fuel at some level. I have seen 87 oct in my Honda quad really gunk up the spark plug and after using 91 it seems to not happen.
I tend to surmise that non ethanol, 91 octane offers me a purer gasoline that not only performs better, maybe, but stores better with less chance of breakdown, separation, or if octane evaporation (alcohol) diminishes grade there is a bump to cover that. Therefore, my choice for all my small engine, and older vehicles that may be sitting around of exstended periods. This could all be faulted thinking, but given the choice at the pump I always go for non ethanol, high octane for these reasons, but otherwise, I’m just happy to have fuel.
So, VW folks, are storage and harsh environments a consideration? |
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