My HCH-06 has gotten an average of 46 mpg for about 3,000 miles. On my latest tank of gasoline, I got the mid-grade (89 octane). Now, after my first 100 miles on this tank, it's 53 mpg. I am thinking that maybe I've finally figured out the EV mode idea, although I really don't think I've got it yet. The other possibility is that the slightly higher octane (89 vs 87) helps the mileage. We'll see how it goes for the rest of the tank.

Has anyone else tried the higher octane gasoline blends? Have you noticed a difference?

 

Go back to 87 and see if the the milage stays up there. If it does then it is probably that the car broke in and you got better driving it.

 

Thanks. Yes, that is the plan. I'd rather not pay $.10/gal extra for the midgrade. I just have to wait a bit, though. I'm hoping to get another 500-600 miles on this tank! HaHaHaHaHa!!...to all you non-hybrid owners.

 

This question has been asked many many times and going with a higher octane results in no improvement whatsoever, but it can result in engine damage (over a long term, I mean). Stick with 87.

That said, it is possible the particular gas you used had different, better degerents and other additives in the higher-octane gas versus the regular grade. But the octane of the gas itself does not help.

 

Thanks, that's good to know. This one was a tank of Shell gasoline. Could be the brand or the batch, I suppose.

I have, however, noticed some knocking when I'm accelerating up a hill with a cold engine. That's another reason for the experiment. I'll know tomorrow morning if the higher octane helps with the knock or not.

 

YES, the higher octane will help with the knock. Almost ANY rotary owner will tell you to use the highest octane availible for this reason. They are very sensitive engines because of the apex seals (2mm thick and what creates the seal for combustion) and detonation (knock) will chip them and in turn from the petriochord movement ruin your housings and lose compression. Higher grade fuel takes a higher temperature and pressure to detonate, and I can say from personal experience, I have always had better fuel mileage from a higher grade gas driving a vehicle the same from one tank to the next. It was never drastic, but around 2-3 mpg from 87 - 93. I could squeeze an extra 30-60 miles out of a 18 gallon tank. I am not saying it is purely the grade itself, it may be the additives like said by CG. Also I have always heard to use higher octane in older engines to prevent the 'knocks and pings'. I have never heard of it ruining an engine from prolonged use though it may be possible. Maybe racing fuels, but I don't see anyone buying 100/110+ octanes for thier cars, i know 5 years ago it was around $4/gal. or more. I personally don't think the 10-20 cents a gallon for different grade gas amounts to much with prices over $2/gal, an even less when you are getting 50+ mpg and fill up half as much as the average consumer. Now, when it was 69 cents for low and 89 cents for premium, that was a different story. I also know that computers are programmed for certain fuels, i had a car that required premium and it said if you use low it retuned itself for (i can't remember) quite a long time, even if you only put a gallon in to get to a gas station, makes no difference. But I am getting off-topic so I will stop

take care and have fun!!!

 

Rotary engines are quite a bit different than piston engines, but yes, higher octane does prevent knocking. Knocking is the result of excessively high temperatures in the engine.

I have heard Shell doesn't add its special detergents to 87-grade but does add them to the others, so that could explain the higher mileage. But Chevron supposedly adds detergents to all grades.

 

The improvement you are seeing is probably due to the Shell gasoline.
http://oilspot2.dtnenergy.com/e_arti...1TSk28,a1SwHkk
Shell gas has friction reducing additives and 5x the normal amount of detergents.
The fuel savings is small, perhaps 2-3% (they don't say exactly), and probably
not enough to justify the extra money they charge for it.

 

well, it basically said 1%. 125 miles more a year based on 12,500 miles in a year. Not too much at all. I wonder how they found this? Through bench tests or through customers driving experience. 5 miles more on a 500 mile tank, could be any factor IMHO . Sounds like a gimmick but if it was a concious effort and the best they could do for now I commend them. But I don't know. It also sounds like they have more up thier sleeve, they said it is the second fuel offering in a series that will provide ... which means to me better stuff in the future or I am reading too much into it. I guess all the cleaners would be good for a new car to keep it clean, but is it not bad for those driving 300k+ mile Hondas? A friend drives a 88 CRX with over 325000!!! Have to LOVE Honda for reliability (and fun).
I have a hard time trusting fuel companies, and it is not like I am always around the same company every time I need to fill up ... but maybe that will soon change when I go from 300 miles on 18 gallons to 600+ miles on 12

 

A 1% FE change is very possible, but you are right to be suspicious without knowing how they measured that. Lots of things could cause a 1, 2, or even 3% change in the real world. Most likely they took some really gunked up engines that also knocked, then used their magic potion on it and looked at the change after a few tanks. Thsi was almost certainly done in a lab, not taking customer data.

Knocking is not due to excessive cylinder temp. Well, it is in a way, relative to the fuel being used. Knocking is the predetonation of the fuel charge- literally the fuel starts to explode before its is sparked...explodes because of temps and pressures that are completely normal, but the fuel itself is too volatile.

Higher octane fuel literally means more octane vs heptane in the fuel- octane having 8 cabon atoms: more chemical bonds, therefore higher ignition temp and later ignition, preventing knocking. A lab tests a fuel mix and compares when it started to knock (under an increasing load) versus pure isooctane and pure heptane fuels.

Now the refinery does not actually add C8H18 to the fuel...the cheaper and most often used way to increase octane is to make fuel "equivalent" to 87, 89, or 93% octane by adding MTBE or ethanol. Pure ethanol has the equivalent knocking of >110% octane gas, so a little bit added to stock fuel brings it up to 89, 93, whatever. Every 10% ethanol added kicks octane up by ~2.5%. Tri-ethyl lead used to do the same thing in "hi-test" gas, for those of us who remember leaded gas.

MTBE/ethanol also has the effect of leaning out the fuel- adding oxygen to meet EPA RFG requirements.

Ethanol is very often also the 'detergent' used in fuel. Alcohol is an excellent solvent and scrubs out the rust and gunk from the fuel system- anyone who has converted an engine has seen their fuel filter clog up very soon after going with straight ethanol. Alcohol also clears out deposits form the injectors and elsewhere, and is mixes with any water in the fuel, preventing gasline freezing or a water slug getting to the engine. A bottle of dry gas or injector cleaner is usually straight methanol- even more powerful solvent than ethanol.

Now, alcohol, MTBE, whatever has lower energy content per unit volume than gasoline. So adding it reduces the energy content in a gallon of fuel in your tank. 10% ethanol reduces MPG in most engines by about 2.5%. If YOUR engine knocks, you're losing more than that anyway, so the higher octance will help improve MPG on balance. But if YOUR 4-stroke piston engine is NOT knocking, the higher octane will not help MPG, other than to ensure your fuel system is clear. Very very few engines have knock problems anymore- a "knock snesor" is standard instrumentation and adjusts spark timing and fuel charge delivery to stop it 99% of the time. An engine that requires premium simply means the engineers painted themsleves into a corner when they designed it, and the easiest way to make sure power performance specs were met was to slap a "premium fuel only" label on it.

So the magic juice is usually Ethanol or MTBE, doing double or triple duty. Pretty magical stuff.

As for lubrication/anti-friction, neither the EPA nor any major manufacturer has noted any change to lifetime, wear, or performance with any change in the "lubricity" of gasoline fuel in modern 4-stroke engines (Ethanol reduces it somewhat, and some folks may add something to counteract that). It is not a parameter that is generally measured exactly because it has so little effect. Any changes that were seen often contradicted each other and/or were so small as to be lost in the statistical noise.

Having said all that, your mileage may vary. If Shell works for you, then go for it. But at least you know what's behind some of the marketing blabber. (For the past few years Shell gets its crude from the North Sea and West Africa- NOT from the Mid-East. Another good point, to some.)