reg vs prem gas query

[randhall]

New owner of a 1976 90/6. Bike is stock, 23,000 miles. Do I need to use premium unleaded gas, or can I go with regular?:dunno Why? Thanks for any/all input. Rand

[skiteach]

I've always run prem in my /5. It hurts these days-11 gal tank!

[bobh41]

To understand octane rating, you need to understand a little bit about how car engines work.

The engine’s power comes from carefully controlled explosions of gasoline/air mixture inside the engine. To control the explosions, the gasoline must burn at exactly the right rate. This is controlled by the gasoline’s chemical composition.

Gasoline is a mixture of many chemicals that burn at different rates. One chemical that burns at the right rate is isooctane. A chemical that burns too quickly is n-heptane. To describe how fast a gasoline burns, a scale was developed using these two chemicals. Isooctane is defines to have an octane rating of 100, which n-hepatine has an octane rating of 0. Octane ratings compare the burning characteristics of gasoline to mixtures of isooctane and n-hepatane.

For example, if a cheap gasoline burned the same way as a 50:50 mixture of isooctane:n-heptane, the octane rating would be 50. Gasoline with an octane rating of 87 burns he same way that a mixture of 87 percent isooctane and 13 percent n-heptane would burn.

from pa.msu.edu/sciencet/ask_st/101696.html

I've always used the highest octane I could find. My /6 began to ping under load (uphill for example in top gear at around 3500 rpm). I had it tuned up and it doesn't ping at all.

[zarinelli]

New owner of a 1976 90/6. Bike is stock, 23,000 miles. Do I need to use premium unleaded gas, or can I go with regular?:dunno Why? Thanks for any/all input. Rand

... minimum octane rating the owner's manual says you should be using. No reason wasting money on higher octane gas - I am pretty sure you won't "feel" a difference.

[Gil]

I use 87 on my R90/6 (1975) and I use a couple of drops of Marvel Mystery Oil in the gas. Just about a teaspoon per gas tank to keep the valves lubricated and the engine smooth. For the last two years I have ran this bike hard and not once I have encoutered an issue.

[PHMarvin]

Hi, Rand,
My first BMW bike was a '76 R90/6, bought new in April '77. If I remember correctly, the owners manual says to run premium, 98 octane leaded fuel. I was transfered to Europe shortly after buying the bike, and it was shipped there. I spent a month in Spain in '78 and many times, 98 octane wasn't available; the best available was 95 octane. The bike didn't seem to notice the difference. Were it me and if I didn't have access to 100LL avgas, I would try running regular. If it didn't ping, fine. That's what I'd run. If it pinged, I'd try mid-grade. Same scenario. Only if it pinged on mid-grade would I think it needed premium.
Ride Safe,

[crazydrummerdude]

I put 89 in my R75/6 last week and it ran like crap through the whole tank. Back to 93 and it runs fine.

:dunno

[Bigrider]

I use 87 on my R90/6 (1975) and I use a couple of drops of Marvel Mystery Oil in the gas. Just about a teaspoon per gas tank to keep the valves lubricated and the engine smooth. For the last two years I have ran this bike hard and not once I have encoutered an issue.

I was told the Mystery oil is also good for lubricating the slides and other friction prone things on the Bings. I use a teaspoon every other tank of gas. Even if it doesn't work, it makes my gas smell minty fresh. This is very important in dealing with other easily offended airheads.:p

Dave H
San Antonio, TGX

[randhall]

One of the factors in my deciding to go with an airhead over other models/brands of motorcycle was the great support network of sharing people. So far my expectations have been exceeded, many times over. Thanks for all your input. I will work through the suggestions, one at a time, to find which works best for my ride.:clap

[PAULBACH]

Go with what MOM (Motorcycle Owners Manual) recommends. The difference in price is not a king's ransom. It is the difference in cost between the least expensive and the middle grade and/or high test. On a five gallon tank that delta is usually less than a dollar.

[Braddog]

I bought both of my '77's used within the last 10 years. Previous owners both said that they always ran the highest octane they could find (92 or 93). I do the same. They both run like tops. No technical details here, just my own experience.

[jdmetzger]

The previous owner of my R80/7 said he used to run mid-grade (89 octane) through the bike. I found it didn't run well like this, so I always ran premium. I wonder if the cheap gas is what led to my premature valve wear. Since getting new valves/seats (and everything else associated with a new top end), I run 87 octane, but that's because my bike is now dual plugged. If it wasn't, I'd stick with the 91 or 93 octane stuff.

[James.A]

I put 89 in my R75/6 last week and it ran like crap through the whole tank. Back to 93 and it runs fine.

:dunno This is my experience also.

[arebin]

My Airheads will ping on anything less than 92.

My Ducati SS900 will run on 87 with no problem.

Run what don't ping.

[The_Veg]

Run what don't ping.

+1

FWIW, my 1995 R100R will run on 87 with no problems at all.

[osbornk]

Run what don't ping.

+2

My 86 R80RT has done fine on regular for the 8 or 9 years I have had it.

[carockwell]

My understanding is that the pre 1981 bikes were mostly built with higher compression and needed premium gas. The later bikes use lower compression and "may" run on 87 octane. With the aircooled Beetles and Porsche's we found that certain cars were always okay with 87 octane, other cars always needed 91 octane, and some cars could use 87 octane unless the weather got hot and then they pinged so 91 octane was used. The aircooled engines are sensitive to heat and load. In warm weather running at relatively high speed your boxer may need higher octane gas. By the way, the old 95 octane gas in the 60's and 70's would only be rated as 90-92 octane today as we use a tougher octane standard now.

[TELLURIDER]

How do you think altitude would play into the equation? I live at 8,800ft and usualy ride between 6,000 and 10,000 it would make sense to me that because of the thinner air that the fuel oxygen mix might be better with lower octane.

[ccolwell]

1) Go with the owner's manual as long as it gives an octane rating used in the US. European octane is calculated differently.
2) Check the compression ration for yours (should be in the manual). I believe it's 9.5:1 (my 76 R75 was). That probably needs hight test. Later bikes went to 8:1, don't know when but my '84 R100 was that.
3) Pinging is the ultimate test, you don't want that.
4) Mileage can be a factor -- carbon build up on the piston can increase compression slightly.
5) Hight test is a bargain. It's always about 10c a gallon more, so it's a better bargain the more expensive gas gets. :laugh

[dougfollett]

Non expert opinion here but what I have heard from reliable sources for automotive engines is that if it does not ping or knock when using regular that it is OK to use it. Some high compression engines will knock with regular. Also not all premium gasolines have the same octane rating. My Caddy says right on the dash and by the gas cap to use only premium. I have used regular for the past 50,000 miles and never had a problem. I also use regular in both my R100RT and my R80RT and they seem to like it. People like to think they are doing something good for their vehicle by using premium but if it doesn't need it, it is a waste of money IMO:blah .

Hoo

[James.A]

The owners manual of my R75/5 states" 97 research octane minimum", or to that effect. I'm guessing that current Shell 93ROM is not quite the same. /6 should be pretty much the same minimum requirement. I can sure tell the difference if I don't burn Shell or Amoco premium. I'm sure there is plenty of science involved here that I,quite frankly, don't understand. The seat of my pants tells me all I need to know on this topic.

[RebeccaV]

My /6's manual calls for a minimum of 98 octane. I got some pinging and my airhead mechanic said that an octane booster wouldn't be a bad idea.

Dunno if it's just snake oil, but I've used it since and no pinging.

[arebin]

My /6's manual calls for a minimum of 98 octane. I got some pinging and my airhead mechanic said that an octane booster wouldn't be a bad idea.

Dunno if it's just snake oil, but I've used it since and no pinging.

Seems like that the /6 manuals used RON numbers only (please correct me if I'm wrong). I reckon that the (R+N)/2 number for 98 RON would be somewhere around 93-94 at US pumps. Doesn't really matter, if that's what it takes to keep it from pinging, I guess that's the answer.

[bearsfolks]

All I can say is that in Colorado the "regular" is rated at 85 octane, mid-grade 87, and premium at 89. It appears that the higher up you go, the lower the octane requirements.

[Isamemon]

well
some call me a cheap bastar*. But on a 6 gallon tank and getting 40mpg I do go for the exta stuff, oh wow, 60 cents
but for me, and this old scooter(30+ years) 60 cents a week is minimal if it makes the bike run right.
It was tuned, balanced and color tuned on the good stuff, so that is where she will stay
Josh

[lkchris]

In the late '70s/early '80s premium fuel was NOT available in the USA. This was before there were three grades of gas, and all the stations used their pairs of pumps for unleaded regular and leaded regular.

Guys with BMWs were in trouble and this is why dual-plugging was introduced by USA mechanics.

In 1980, BMW finally lowered the compression of its bikes sent to the USA so they could use regular fuel.

All bikes built before 1980 require premium fuel except for a few exceptions where thick cylinder base gaskets were installed.

[lightning]

If you use premium (93) in an engine that doesn't need it, can you hurt the engine? (overheating, for example)

[tghsmith]

no, your just paying for what you don't need and can't use. keep the rpm's up 4200+, most bikes will ping if your in top gear at 3000 and roll on hard. Mountains,loaded heavy and or damn hot wheather I might jump up a grade.

[keelerb]

Using higher octane than you need not only wastes money, but will cause faster/heavier carbon build-up than using the proper octane (i.e., the lowest octane that will prevent pinging) would. - B

[lightning]

One of the best mechanics I have ever known says that you can't always "hear" the pinging. For that reason, he recommends 93 octane even if you are not sure what the bike needs.

[terham]

Go with what MOM (Motorcycle Owners Manual) recommends. The difference in price is not a king's ransom. It is the difference in cost between the least expensive and the middle grade and/or high test. On a five gallon tank that delta is usually less than a dollar.

I put premium in my /5 based on this. It doesn't cost much more to use the higher octane and I figure it doesn't hurt, even if it isn't necessary. Nothing's too good for Heinrich.

[Friedle]

Remember when your MOM was giving advice as to gas type, it was talking about leaded gas, not the stuff we use today. Even if you can't hear the motor pinging, you can often see the results of pinging on the sparkplugs if the problem is severe enough....or maybe those large holes in the pistons might just be a clue.
Any grade higher than what is required to prevent pinging is just making Exxon/ Mobil richer than they already are while not really doing anything for you.

=8^)

<snip Nothing's too good for Heinrich. >

Why would your gas TANK really care what grade of fuel it contains???

Friedle

[RJM2096]

Remember when your MOM was giving advice as to gas type, it was talking about leaded gas, not the stuff we use today. Even if you can't hear the motor pinging, you can often see the results of pinging on the sparkplugs if the problem is severe enough....or maybe those large holes in the pistons might just be a clue.
Any grade higher than what is required to prevent pinging is just making Exxon/ Mobil richer than they already are while not really doing anything for you.

Besides looking for pinging, look for run-on conditions when you shut down the engine and hard starts when you immedialty try a restart after only 5 mintes of shut down. These kind of issues may be saying "use a higher octane".

Some advanced engines even have dynamic timing that eliminates knock. But timing that is retarded will cut your gas milage.

[picaresque]

My '75 R90/6, with a 9:1 compression ratio, runs really well on 87 octane regular. My '78 R100RS, with a 9.5:1 ratio, also runs well on the same gas. By contrast, my 2004 R1150GS with a 10.5:1 compression ratio, runs like **** on anything below 93 octane. It is currently for sale.

Of course, YMMV.

[JREDFORD131730]

I find this all very interesting. I have owned three R bikes (1100, 1150 & 1200) and have only used premium gas when I had to, with no problems. My 2005 r1200RT had 45,000 miles on it and runs great.

BTW I have owned Mercedes sedans ans sport coupes with much the same experience. I currently drive a 2000 Land Cruiser which recommends premium gas and also only drinks regular.

At a quarter a gallon cost difference there is no telling how much money I have saved over the years.:dance

[kentuvman]

Google top tier gas - it will take you to a website that recognizes oil companies who exceed mfg. standards. I have good luck in MN with Shell V-Power for my
F650 and also unoxygenated premium (no Ethanol). Ethanol is not good for any carburated engines.
I buy regular in my Honda & Durango but when it comes to my Beemer, I want the best possible performance.

KT

ps - Shell V Power is the official gasoline recommend by Ferrari and just recently, Harley Davidson. It is a good product.

[picaresque]

Practically all gas sold in the U.S. is essentially identical -- except for the octane. For years, gasoline has been shipped throughout the States via the same pipelines, regardless of the brand name of the station that sells it retail. Not only is this this the safest way to transport fuel, it saves the distributors money. Once the different companies collect their product from the pipeline, may will add their own additives, but these really don't affect how it burns in your engine.

I buy the cheapest gasoline I can find. The brand name at the station doesn't matter.

[20774]

That's what I thought, too. One of my co-workers said his newish Corvette didn't like Chevron gas...the on-board computer would send him "nasty notes" about functions in the engine that weren't correct. So he switched gas stations (not sure to what) and the engine is now fine.

On my 2000 Corolla, I've been having some pinging...engine has 100K miles. I've been using Chevron gas almost exclusively. I tried a higher octane and that helped but only very slightly. I recently began to fill up with Shell and the problem has gone away. And my gas mileage has gone from a solid 33 mpg to a solid 34 mpg. And that is even with the winter blend, if they have such a thing here in South Texas.

I'm going to stay with Shell from now on in my vehicles, including the /2 and /7 (OBMWC*).

* Obligatory BMW content