Fuel Grades
 

Ok, who uses regular gas, and who uses premium? If you use premium have you noticed an FE difference in the two?

It depends. I buy regular for the Elantra and Shell V-Power (premium) diesel for the TDI.

i choose regular for my cavalier, but when i had my focus i had the ecu flashed and could only use premium.

im going to on the next two tanks however give premium a shot and see if there is any difference, but i look at it as regular is cheaper, so it would have to be a great difference in FE to make the complete switch.

I use 89 in my DD an 87 Turbo Volvo. The owners manual says 91 but since I hardly ever go into boost why should I spend the money on octane I'm not using. 87 makes the car run poorly and it has pretty poor pick up if you have to put the pedal down.

I've used both premium and regular in my bike and have noticed no difference. The manual says use premium, but I have a small engine that just doesn't have the compression to completely burn premium.

Will -

I ran Chevron 91 last year because of my HAI (hot-air-intake => lean-burn => higher octane is better to avoid knocking/pinging). I switched to 87 when the gas prices got too high, didn't notice a change, and never switched back.

I have a hankering to up the octane again because my car is *different* from last year. I also think it has been on 87 for so long that I might be able to detect a difference in the way it drives (big *shrug*).

CarloSW2

Even if it did yield better FE, from a cost perspective it would have to make up for that 20 cents or so per gallon to truly make it economical. I wouldn't mind seeing some data on it. I'm not quite sure it's worth the gamble of higher fuel prices for few tanks, personally. I'm sure it's been looked at before somewhere.

Bailout at CleanMPG, with his commute up and over a rocky mountain pass in a Yaris, tested this.
regular was best
-4% mpg with midgrade
-9% mpg with premium

I think I'll stick with the cheap stuff.

When I had my HAI (160F) I used premium to prevent detonation, but the cost-benefit was off. Now, intake temps are 100-120F with full advanced timing and no ping with near-full load (some knocking at high RPM, so I don't go there much).

The TSX "requires premium", but runs just fine on regular. The savings add up. FE is the same too. There's a bit of stumble from time-to-time at 6k RPM with VTEC, but again, very rarely used.

Long live 87!

RH77

In my 11 years old turbo diesel I used only regular and mid-grade during years.

One of the rules to eco-drive is to shift up soon, but it had difficulties to stay at 1500rpm. During the first premium tank I felt changes and now (at 4th tank) it can accelerate from 1200-1300rpm.

Because it permits me to improve my eco-driving style premium permits me to have a better mileage. Currently I'm staying with the premium as while I'm saving 33% of diesel, I'm saving 30% of money. May be one day it will be the placebo effect... My mechanic maintains my car, but premium seams doing things my mechanic doesn't...

Denis.

groar -

I only see one grade of diesel fuel in the USA (but maybe that is because I don't have a diesel car - I am not looking very hard). Can you tell me the difference in the diesel grades in France?

CarloSW2

Some of these responses have been very interesting. I have been using nothing but regular after my engine rebuild so I could break it in on regular. I have been thinking about going with premium every few tanks to help clean it out.

I would have expected people to see more of a difference in FE between the two.

I'm not sure which would be cheaper, but running a tank with the "Seafoam" additive might help clean the fuel delivery system. Every year or so I run it through the brake booster line to clean the top-end. LOTS of white smoke, but that's just the carbon build up burning-off. Others recommend Auto-RX (never tried it) -- I like Seafoam because I can find it on the shelf at the auto parts store. It's great stuff.

RH77

Do you add it to your tank or pour it in the engine like others do?

That's ironic Will, I just topped off today with midgrade to see how it affects my metro. It'll take about a week to see, After that I have a couple of gallons of acetone (99%) laying around, I'll add a couple of ounces every tank. We'll see....

I run 87 in everything all the time except if I go racing

I used mid and prem a few years ago and couldn't tell a difference from 87 in power or mpg and figured I was just wasting money. It has been regular since.

Both -- mostly through the booster line directly to the engine.

I perform routine maintenance and tune-ups on friend's and family's cars -- they just bring them over to "Rick's Garage". All of them get the Seafoam treatment in the tank and through the booster line.

One success story is on a low-mileage '95 Mercury Mystique 4-cylinder/auto. It's driven 5 miles/day to and from work. It was REALLY gunked up with carbon. The idle-air control valve got loaded-up and the idle speed was abnormally low -- shook the car like crazy. Either the treatment was to fix it, or replace it (difficult spot on the underside of the engine). So far, the Seafoam (and 10 miles of white smoke) did the trick.

One gunk preventer I have on the 'Teg is a PCV catch container. It's basically an air compressor moisture collector, attached inline between the PCV valve and the intake...

87 in the festiva. 92-93 in the turbo cars. I think we put reg in the shadow once and it gulped it down. I kinda wanna try a tank again just to see but im scared. Its also non intercooled with cast pistons so I do *not* want to detonate with it.

I use premium fuel in my car because for some reason, Christine hates regular. When I run regular, the car pings going under load and feels weak. I thought I had a timing issue at first and messed with the timing like 27,000 times and found no difference unless I went way out of specs, but this caused idle issues and other problems. I decided to run premium for the hell of it and within 10 miles, I noticed better throttle response and that damn pinging (valve clatter, fuel knock) went away. I have been running it ever since and stick with one gas station when possible.

I heard all the bull from techs about 1996 and newer cars only need regular because the PCM controls the timing, blah, blah, blah. I believe that to a point, but this does not go for all cars in my opinion.

I also figure this. Premium is usually 20 cents higher than regular per gallon. My car takes 10 gallons from empty and that would equal $2.00 on a fill. I would pay that extra so the car is not subjected to any harm. As far as fuel mileage increase goes, I did not notice a change myself when I switched, but feel more confident about what's running my engine.

If your car runs fine on regular, then save the $ and use it.

One more note.

I do not use fuel additives, but I do use Seafoam. I buy a can and dump 1/3 in the motor oil when there is about 500 miles to go for service, another 1/3 into the fuel tank, and the last portion gets sucked right down the throttle body while the engine is running and my hand is on the throttle to keep it from stalling. After you get it all into the TB, shut off the engine and wait 5 minutes. Then go on a drive and watch the smoke! It may be very severe at first, but eventually clears out.

There is an old trick they use on the Crown Vic police interceptors where they spray water into a hot engine through the throttle body. Carbon cystalized in the combustion chamber will actually shatter when the water hits it and it breaks up and is expelled out the exhaust. I have done the water trick before, but I prefer the Seafoam since it offers lubricity and will not harm the engine in any way.

Well I vary between 87 and 89. Mostly 89 so thats what i voted. On 87 or regular it will ping or knock, well at idle at least The engine is whooped anyways, it'll knock and rattle on accel and burn blue/black smoke. It isn't a diesel but it looks and sounds like one

Johnny- Thanks for all that info. I will certainly give that a try. I never hear of using sea foam in the oil, but it sounds like a great clean out. Looks like I got more work to do.

That looks like a great contraption. If I can find one at a good price I may do that instead of my "redneck breather"

According to API, premium and regular gas has essentially the same BTU content (111,400 BTU/gal). Premium is needed on high compression engines because of knocking, but "normal" engines won't see any consistent benefit. Some sources say that the BTU content of premium is slightly lower than regular.
Carbon deposits in the engine, usually high mileage city driven engines, can reduce the cylinder volume (increasing compression), causing knock. But that's a pretty poor reason to spend an additional $0.30 per gallon when Sea Foam can take care of that.

I got mine at Home Depot -- Wal-Mart may have them cheap too.

Here's the instructions on how to do it. Pretty simple, just remove the foam insert, get some screw-in hose nipple connectors (often in a package set) and hook it up. I dump mine out at each oil change.

Mr. Mullet: I'm glad a respected mechanic does the 1/3 trick as well. I heard about the cop-car water treatment, but I trust Seafoam for the lube and combustion. I generally dump it in, feather the throttle, and dump in a bunch to let it stall and sit for 5-10 minutes. I explained to my neighbors what the "fire" was all about when I first did it, though :o

RH77

I use premium in my Matrix. The engine has a 10.5:1 compression ratio but Toyota says regular unleaded is fine due to the design of the cylinder head. It seemed more responsive when I started using premium. The deal was sealed on a couple long uphills that always required a downshift. I don't need to downshift anymore. I don't know how it's affected my fuel mileage as I started using premium before I started ecodriving.

Talk about overwhelming. Maybe we should all buy stock in Seafoam. :thumbup:

RH77-Thanks for the "how to" I will most certainly use it!

Not to throw a wet rag on you seafoam guys but I have to wonder about all that smoke you are pumping out. What is in seafoam and what happens when it burns? Sounds pretty nasty to me.

BTW the water injection thing works well at removing carbon build up and does not harm your engine provided you don't dump a bucket over your intake. The best thing? No extra pollution.

Something to think about...

I have been drag racing fwd cars since 83 and always have looked or better FE. On EVERY car that used reg fuek, they all slowed down when I put in higher octane. Higher oct burns slower and with out having a motor designed for it, it's not needed. HOWEVER....my SRT4 requires it and when it was bought in Feb I used reg in it....got 26 mpg best at a constant 65 on interstates.....in April I started using 92-93 due to racing season and the FE jumped up to the EPA 31 rating. There was no driving problems with the reg, but power went way up in the seat of the pants area with the switch.

I use regular. I tried one tank with premium, and got relatively lousy mpg (29!). Despite the relatively high compression (~10.5:1, similar to the Matrix/Vibe), it seems to run best on cheap gas. E10 may or may not be an issue with the 1NZ-FE, as well. I'm sort of currently studying that.

Interestingly, I get my best tanks with Indian reservation gas, as it generally doesn't have ethanol, and racists insist that it's "watered down." Plus, it's generally $.30/gal cheaper than everywhere else.
...never mind that you can't water down gasoline. High school physics/chemistry is apparently beyond the grasp of the average person.

Regular for me, we get ripped off in Canada as they charge at least 10 cents more per litre for premium which is 38 cents a gallon. Also my beaters certainly don't require premium and the price gouging isn't offset by any possible mileage gains.
All my small engines get premium as they don't have knock sensors to retard timing if needed for some reason, plus gas for them is a very small percentage of their operating cost and premium doesn't have ethanol in it. Ethanol attracts water which could be bad for things that are only run once a month.
Ian

Hmm... I use the cheap stuff in a 98 1L metro (and everything else) and use plenty of throttle. I can only make it ping when I advance the timing too far. <shrug>

Hey, are you on BITOG? LOL

Yeah, I've read some of Bob's stuff :)

I'm not trying to sell the product if that's the implication. Use Auto-Rx or similar solvents to achieve the goal if the People want choice.

I change the oil every so often. Usually when it's a quart low, it's time (5-7k miles). The catch can is there to prevent the gunk.

I tinker with cars for fun (and it saves people money -- unless I break something and call in a real mechanic :o)

RH77

For me, it is Octane 89 for the Matrix and 91 for the MB E Class. I have for a couple of times used regular fuel on the MB through mistakes of my own or those of the men/women serving at the pump despite that the manual says premium fuel only (don't laugh, in Richmond, BC, there are no "self serve" pumps:)). No issues whatsoever. I presume that the MB's ECU has adjusted to cope. I have also used premium fuel on a former car, a Yaris, which only needed regular fuel, and noticed no difference in the FE.
There are many factors that can affect a car's FE and my personal experience with just a few tanks can hardly help conclude anything.

You're obviously a corporate shill. Go back to your cave!

Seriously, the catch can is the giveaway. I have one, too. Tee hee.

It's an excellent site, and I for one am not afraid to proclaim it's awesomeness.

Bob Is The Oil Guy

Between the great tribological minds there and the great economical/aerodynamic minds here it's like Harvard & MIT.