I realize this is slightly off subject but I wanted to see what responses would come out of it. I own an 81 Honda CB750 Custom (motorcycle).
I have heard two things, the first being comments about high compression engines and since motorcycles by nature are high compression you should always use premium.
Second; motorcycles are an air cooled engine that can burn to hot very easily. Premium tends to burn a bit to hot on the engines and the bikes seem to run better on regular where there are a few impurities.
In my own experience I found the bike runs about the same on both though I don’t know if one is hotter than the other if you touch the fins after a ride you get burnt and it hurts in both cases :).
Any opinions on this? I want to do what is best to keep the bike running as it is rather vintage as motorcycles go.
First, motorcycle engines are not higher compression by nature. They are, like any other IC engine. In general they are higher revving than car engines, but that’s not the same thing. Second, higher octane has nothing to do with the amount of heat produced by the fuel. It is only a measure of the fuel’s resistance to premature ignition.
I’m pretty sure all the Hondas from that time frame ran on regular, but you might check on a Honda motorcycle specific discussion group. Just be aware there is a lot “old mechanics’ tales” floating around out there.
Joseph has the best answer. Premium is to be used only in higher compression engines that call for it. It’s a total waste of money for all else. All gasoline has plenty of cleaners in it. The ONLY advantage that premium serves is it’s higher octane to avoid pre-ignition (pinging) in the high compression in the cylinder, period.
Either carbon buildup increasing the compression ratio, or a slipped distributor that has greatly advanced the timing. It’s not easy to fix the first, but the second is easy to check.
I want to throw in a wrench in your discussion. I live in California and we have three grades of octane. We have the low 87, medium 89 and of course, 91. I always use 87 in my '98 Camry 4 cyl. Would going up one grade change anything in performance or mileage?
It depends on your car. If you are below the optimum right now, it will help, if you are above it will not help and if you were almost too high, it could actually damage it.
If a high-performance engine is running poorly on premium (and you’ve tried several brands to make sure it isn’t a case of mislabeled gas), you should take it to a mechanic to see what’s wrong with it. The timing could be way off, or some part of the smog plumbing not working, or the knock sensor is constantly reporting knock when there isn’t any…
Some older vehicles have had problems with ethanol dissolving certain rubber or plastic parts in the fuel system. The owner’s manual may or may not address the maximum allowable percentage of ethanol in the fuel. If it doesn’t, ask the dealer. I would think that a '96 would be able to handle at least 10-15%, but maybe not.
High-compression/blown engines usually specify a higher octane. If it has a knock sensor, that may have retarded the timing (on regular) enough to eliminate knock. The price you pay is that the engine is now less efficiently burning fuel, and producing the carbon (soot) you see. Switching to premium puts the timing back in the “right” place and runs more cleanly.
When I was shopping for my car (Acura TL) I asked two dealers about using regular. They both indicated that it was ok except that it may cause damage to the catalytic converter. If using regular instead of premium voids my catalytic converter warrantee that could result in a big cost. Is it true that using regular in a car calling for premium could damage the emissions system?
Think about it- you’re getting 15% less energy (when compared to “gasoline”) from only a 10% fraction of the total fuel volume. What’s that, something like a 1.5% reduction in available energy? 15k miles/yr @ 34 mpg works out to around $20 more per year (@$3/g) for gasoline with 10% ethanol. Big deal.
Compared to a reduction in hydrocarbon output, less dependence on foreign oil and a water absorber to boot, it’s a small price to pay IMO.
I’ve never heard such a thing, but if the manual calls for premium, using regular may void the warranty for associated parts. Wonder if they could prove you haven’t been using premium!
I had a 91 Ford Ranger (4x2, 4 cyl, 5 spd) that I ran regular fuel in from when I bought it in 2000 until 2002 when I noticed knocking and pinging on hills. I then switched to premium and noticed better performance and the knocks and pings went away. I was happy with that so cost did not matter. In 2003, I moved from Buffalo, NY to Portland, OR and drove said truck packed solid with all my belongings. The truck ran great, even in the mountain passes totally loaded. I arrived in Portland and continued to use premium until gas prices spiked, at which time I returned to regular. A very short time after the switch, the knocks came back but worse than before and at intermittent times. One day, on the highway, on a hill, the knocks became louder than ever, then the truck lost power and the engine blew.
So my question is…will running a non-high compression older engine such as this on premium for a few years and then switching back to regular eventually cause it to self-destruct? In this case, I believe it did.
NOTE: I regularly maintained this truck (oil changes, filters, etc).
Sounds like an alcoholic switching to liquor to keep happy then having to switch back to beer. It may have been that the gas you got in Portland was lower octane than you had in Buffalo, hence the worse knocking. Maybe in addition to the motor being older made it break, who knows.
It is called octane creep–the added compression due to carbon buildup in the combustion chamber. Sea foam can help remove it–read the can carefully–as well as several others. Also, compression ratio is not always a reliable factor in determining ping-a-bility. As an example, someone built an extremely long rod/high compression ratio motor which ran on regular gas. It had good heads–ie efficient parts AND combustion chambers. It is possible for an 11:1 motor to ping less than an 8.5:1 motor.
You may “loose”(sic)performance using regular in an engine that speciifes premium, however it WILL NOT harm the motor if the knock sensors are doing their job! These sensors detect detonation and retard the timing. Many premiums also have a double dose of cleaning additives (Shell & Chevron).
BTW, not all gasolines are equal in quality, i.e. have the same amount of cleaning additives. Buying el Cheapo gas, is a false economy. To see a list of gasolines that have double the amount of cleaners required by the EPA in ALL grades go here: http://www.toptiergas.com/
All gas has mandated(US) levels of detergents. Very few if any cars are going to need more.
That is just factually incorrect.
Those levels have dropped by up to 50% since 1995. The “top tier” standard was set by BMW, General Motors, Honda, Toyota, Volkswagen and Audi. The purpose was to prevent carbon deposits on intake valves and injectors. These gasolines cost no more in my area than the “no-name” brands. They have at minimum, double the detergent additives required by the EPA in ALL GRADES. Some of the premiums have even more, i.e. Shell’s “V Power” has 5 times the EPA minimum.
TOP TIER Gasoline Retailers:
QuikTrip
Chevron
Conoco
Phillips
76
Shell
Entec Stations
MFA Oil Company
Kwik Trip/Kwik Star
The Somerset Refinery, Inc.
Chevron-Canada
Aloha Petroleum
Tri-Par Oil Company
Shell-Canada
Texaco
Petro-Canada
Sunoco-Canada
Several years ago when I owned a lumina sedan with a 3.1 I tried all three different grades of gasoline. it turned out the regular and premium gave me the same MPG, but the mid-grade incrfeased my MPG by 11%. Enough to pay for the price increase so I stuck with mid-grade.
Now I own a Colorado with a Vortec I5 and am trying the same test. So far, regulag gets 17 MPG (combined city?highway) and mid Grade gets 20 MPG (combined). I have not owned it long enough to test premium.
As an example, someone built an extremely long rod/high compression ratio motor which ran on regular gas. It had good heads–ie efficient parts AND combustion chambers. It is possible for an 11:1 motor to ping less than an 8.5:1 motor.