Higher octane for better mileage?

[Skydaver]

Originally Posted by Draigflag

It's refreshing to chat to someone open minded like you my friend. Just last year I questioned the obsessive oil changes in the US as at the time, I didn't understand why the same cars here would require such little oil. This one guy sent a barrage of abuse, insulted me and my car and basically said he wanted to run me over in his enormous truck. Still makes me smirk today!

I'm not sure about the big semi trucks here, I should imagine they go by hours too, although I read on a manufacturers truck website that they do 60,000 between oil changes. The biggest interval I've seen for a light passenger vehicle is probably about 30,000 miles, on average it's around 15,000 to 20,000 with the modern synthetics, but it does recommend sooner if you've been "racing" or driving in dusty environments. I try not to talk guns here, it's a sensitive issue in the states. I mentioned it once and got shut down, I guess we should stay on topic

I'll ask my brother about the oil change interval on his rig. He drives a gasoline tanker, with a couple of million miles behind the wheel. I do think that part of the reason the large diesel rigs go so long between oil changes is that they have such a large capacity oil sump (or tank, if they use a 'dry' sump). IIRC, it is very often over 10 gallons of oil per change.

They probably go by hours, not miles, because there is such a huge variation. An OTR truck will rack up many more miles/hour than a short haul truck.

[trollbait]

Originally Posted by Skydaver

A fuelly noob pipes up here. I just sold a 2002 Maxima, 6 spd manual, that I bought new. I put 145,000 miles on it, and kept track of my mileage with an Excel spread sheet.

Just before I sold it, I decided to try an experiment. I ran 2500 miles on regular (87? 89?, whatever) octane (Nissan specifies premium.)

Now, the previous 2500 miles on premium, I wasn't quite as mindful about fuel economy, and it was a different season, but ...

I got 1.3 mpg better on regular.

On regular, I did get a very slight knock on a low rate acceleration that was quickly stopped by the ECM. Heavy acceleration had no knock at all.

So, IMO, use the cheapest fuel you can. Once in awhile, run a tank of a name brand premium through, not for the extra octane, but for the detergent mix that it has.

The different season alone can have a big impact on fuel economy. Amoung other things, warm weather reduces the warm up penalty. Summer blend gas also contains more energy than winter blend.

Then there is the possibility that the premium gas uses ethanol to raise the octane, which also lowers the energy content. On top of that, most cars calling for premium fuel are more performance orientated than for efficiency.

I was just thinking about how premium gas also tends to have better additives. A bottle of additive added to regular should provide the same benefit. it might even be cheaper if you use the dosage amount for your actual tank size.

[Skydaver]

Originally Posted by trollbait

I was just thinking about how premium gas also tends to have better additives. A bottle of additive added to regular should provide the same benefit. it might even be cheaper if you use the dosage amount for your actual tank size.

Now that you wrote that, I'm thinking that my brother in law (the tanker driver) said just that. If your engine doesn't knock on regular, just use an additive to help clean out the injectors.

Gasoline is fungible. The tankers go to a depot, punch in a code, and the gasoline & additives specified by the code are pumped into the compartments of the tanker. Off they go to a Shell station, or Speedway, or BP, or whatever. BTW, BP is working on getting out of the retail business.

Mid grade is sometimes mixed at the depot, and put into a compartment of the tanker, sometimes it is mixed by the pump. I don't think that it's made at the station by pumping premium & regular into the midgrade tank, but I'm not positive.

[litesong]

Originally Posted by VanCollector

On a newer vehicle designed for ethanol fuel, you likely won't notice much difference.

Gasoline engines(supposedly modified for ethanol) only have parts that won't get eaten up by ethanol. As I've stated above:

114 octane ethanol needs high compression ratio (16:1) ethanol engines to extract ethanol energy efficiently. 87 octane, low compression ratio(9:1 to 11:1) gasoline engines can't extract ethanol energy efficiently, but works efficiently with 87 octane 100% gasoline.

[SteveMak]

I saw a wonderful explanation of higher octane benefits on a YouTube video (sorry, can't remember which specific one). Here's the summary:

• You might get more power (various cars, domestic and imported, were tested)
• You might get a little better fuel economy (various cars, domestic and imported, were tested)
• In none of the cars tested (various cars, domestic and imported), running higher octane fuel resulted in saving money.

The only way to know for sure is to run a series of tests in your car. The difficulty is in coming to an accurate and meaningful conclusion, because if you've ever graphed your fuel economy using the same fuel each time, you'll notice considerable differences due to a variety of variables. It'll be hard to eliminate all those variables and attribute the change in fuel economy to the type of fuel you burn, unless it results in a substantial and consistent change.

Best wishes with your experiments.

[trollbait]

I just filled up mid grade, 89 octane, which appeared to give most of the benefits of premium. I only did so because the price gap with regular has been dropping. It was 14 cents more per gallon. That is on the high side of the benefit being worth the extra price per gallon.

10 cent more for mid and 25 cent more for premium is the price point at which the Sonic will have a chance of getting better cost per mile than regular.

[14Corolla]

Ran into a new idea today.
Guy says his wife's Toyota Truck does best with 1/2 Regular, 1/2 Premium. This is the small truck with a four cylinder.
Talking E0 fuel only.
Our E0 Regular is only 85 octane.
East River with lower elevation it's 87 octane.
He say's this is better than all premium.
I think I'll give this a try.

[R.I.D.E.]

I run the cheapest regular I can find. Last tank 3.3 cents per mile.

[trollbait]

Originally Posted by 14Corolla

Ran into a new idea today.
Guy says his wife's Toyota Truck does best with 1/2 Regular, 1/2 Premium. This is the small truck with a four cylinder.
Talking E0 fuel only.
Our E0 Regular is only 85 octane.
East River with lower elevation it's 87 octane.
He say's this is better than all premium.
I think I'll give this a try.

Midgrade is just a mix of regular and premium; either in a separate tank when delivered, or at the pump when dispensed. 50:50 would be a little higher octane than midgrade, though.

On the subject of mixing fuels, E30 to E40 might have a higher efficiency per btu than straight gas. If E85 was available closer, I had hoped to experiment with it in the Ranger.

[14Corolla]

Oh yes. Am well on my way to 40mpg for daily driving and I don't know how much more?!
Just got 39.3mpg daily driving. This tank had regular 85 octane E0. Almost no ethanol left. Maybe .3%?
Last tank was 2 to 3% ethanol left in it. Got only 36.1mpg. Same driving.
I can claim that with no ethanol. Am getting 20% better mileage. !

I still haven't put the P7's on the car. That's a gain on maybe a couple mpg?
I still drive through fast food and idle. That' a waste of fuel.
Otherwise pretty good driving for mpg.

Now this time. I put in 50% premium E0. With 50% regular E0. I estimate with what was in the tank. Probably a octane of 87? Pure 50/50 should be 88.5. The little I drove it. Feels more solid and stable. More solid stable acceleration. I'll see how this works out.

I'm happy as can be! Definitely have 40+mpg in sight! Yes! That's just for daily driving. Don't have any idea how good highway mileage will be. I can go years without doing any of that. hehe