K75rt gas ?

[tinytrains]

The Jetronic system is not smart at all. It was the first popular fuel injection system, not even digital as I understand. Very simple but has it has worked flawlessly for 22 years on my K75.

When my bike was new, it did not like regular and would knock under load. Now a days, it runs on regular just fine. Either the fuel is better, or the compression is lower. But given premium is only $0.80 a tank more, I give it premium anyway.

 

[bikerfish1100]

The Jetronic system is not smart at all. It was the first popular fuel injection system, not even digital as I understand. Very simple but has it has worked flawlessly for 22 years on my K75.

When my bike was new, it did not like regular and would knock under load. Now a days, it runs on regular just fine. Either the fuel is better, or the compression is lower. But given premium is only $0.80 a tank more, I give it premium anyway.

short vision. how many tanks do you go thru a season? enough at $.80 to pay for a tire? maybe just enough for a few free tanks of gas? regardless- if regular works fine, than any amount of $ spent on premium is a waste of $, even if it is "only $.80 a tank more".

 

[breyfogle]

.... Either the fuel is better, or the compression is lower.

Or, .... the bike has tought its rider when and how to avoid knocking and the learning process has been so gradual you're not even aware of it. I.m pretty sure the fuel is not better !

 

[tinytrains]

short vision. how many tanks do you go thru a season? enough at $.80 to pay for a tire? maybe just enough for a few free tanks of gas? regardless- if regular works fine, than any amount of $ spent on premium is a waste of $, even if it is "only $.80 a tank more".

First of all, IIRC, my manual calls for premium. Just because you don't hear knocking, does not mean it is not going on.

Second, the bike is in semi-retirement. I buy a tank of gas for it every 2 months. That is $4.80 a year. Given the long time the gas spends in the tank, I want the higher rating to compensate for degradation of the fuel.

Third, IT'S MY $0.80!

 

[Paul_F]

First of all, IIRC, my manual calls for premium.

I don't the difference between the K75s and K100s, but my manual states states premium fuel for my K100.

 

[bikerfish1100]

First of all, IIRC, my manual calls for premium. i don't recall exactly either, but everyone above that looked in their manual said 87 pump grade is the spec'd fuel. Just because you don't hear knocking, does not mean it is not going on.

Second, the bike is in semi-retirement. I buy a tank of gas for it every 2 months. That is $4.80 a year. Given the long time the gas spends in the tank, I want the higher rating to compensate for degradation of the fuel. THAT i will agree with. and at $5/yr, you're not losing much for that purpose.Third, IT'S MY $0.80!

true- but most of us do ride a bit more than just 6 tanks a year. that's one good day for many. sorry to hear of your affliction.

 

[osbornk]

First of all, IIRC, my manual calls for premium. Given the long time the gas spends in the tank, I want the higher rating to compensate for degradation of the fuel.

Third, IT'S MY $0.80!

How does premium have a higher rating then regular? Premium gas burns more slowly than regular. That would make me think that regular would be better than premium for a seldom used bike.

 

[tinytrains]

true- but most of us do ride a bit more than just 6 tanks a year. that's one good day for many. sorry to hear of your affliction.

The K75 is is semi-retired because I ride my R1200R several days week. No affliction, I just don't have the heart to part with the K75 after 22 years.

As for which octane rating lasts longer, I have no real idea. Just doing what the book says.

 

[tinytrains]

Ok. I just checked my 1988, K75 owners manual, and on page 15, it a says "use 91 octane minimum".

I seem to recall reading that later model K bikes had their octane requirements reduced, but I have no data on that.

The question here was "What fuel are you using". I simply answered the question for my own bike. I never told anyone what they should be using. You can fill you bike with whatever you chose, but I chose to follow the instructions.

 

[35634]

ummm, you're right, but mine sez 91 octane ROZ minimum. ROZ is the German octane rating and runs about 4-5 points higher than US rating. (91 is regular in the fatherland)
So 87 should be fine. Which is good, cause that's what mine has had for the last 26 years.

The manual also states that the bike may gag on alcohol enhanced fuels.

 

[tinytrains]

Well, it would be a great help if BMW would provide units useful to their target customers in their manuals. I am sure I am not the only person misled by this. May as well leave it in

 

[osbornk]

We don't think about it much but elevation has an impact on the grade of fuel you need. I ride at elevations between 2,000 and 4,500 feet and use regular in everything. Back in the day when we adjusted the ignition timing manually, I adjusted the timing on my vehicles "by ear" for the best performance. I would advance the timing to where it would ping and then set it back just enough for it to stop. When I would go to lower elevations, I would get ping until I went back to the mountains. I also remember that the humidity levels had an impact on whether I would get pinging or not. I'm not sure but I think low humidity was when I got a slight ping.

 

[bikerfish1100]

Premium gas burns more slowly than regular.

not exactly. higher octane fuels resist combustion, and thus will not pre-detonate as readily. That pre-detonation is the pinging or knocking that we don't want to hear. However, once the burn is begun, their burn rate is identical to a lower octane fuel.
from what i've read, a higher octane fuel (assuming same levels of ethanol- preferably low to none) will, when in storage mode, remain stable and combustible for longer than will a lower octane fuel.

 

[Paul_F]

from what i've read, a higher octane fuel (assuming same levels of ethanol- preferably low to none) will, when in storage mode, remain stable and combustible for longer than will a lower octane fuel.

Here in Ontario, Shell V Power has no ethanol (if one believes the info on the pumps). Not only do I use this in my two bikes, but also (with stablizer) for the snowblower, lawnmower, leaf blower etc. to ensure that my gasoline quality lasts as long possible.

 

[WalterK75]

I asked PetroCan about ethanol in their gas. The only gas they sell without ethanol is Octane 91 Super Clean and only if it is sold at a PetroCan station which does NOT sell Octane 94. I have been using 91 and 94 in my 1991 K75. Better response than with lower octanes, although with lower octanes I did not notice any pinging or other problems.

 

[kobukan]

I run premium in my beemers, but for me it's more about the additives than the octane, and for that reason I also only run fuel from the retailers listed here. In the northeast I buy only Shell V Power unless I absolutely need fuel and can't find a Shell station. In the southwest I'll go with either Shell or Chevron, there seems to be an abundance of both there (we don't have Chevron in Maine).