Using mid-grade gas

LeoC2

LeoC2

Registered
With the prices they way they have been I've begun switching to mid grade octane fuel. So far I see no ill effects. Has anyone else done this and experienced any problems?

Also, I recommend checking out this site, it can save you quite a bit www.gaspricewatch.com
 
RE: Using mid-grade gas

I use mid-grade in the winter ONLY. If I use anything less than 91 in the summer when it's 80+ outside, I can hear mild detonation (pinging) - especially when ascending hills.
 
RE: Using mid-grade gas

If your car is pinging, the knock sensors must not be working properly.

All the reading I've done on this subject suggests you will lose performance(a given) and mileage. The loss of mileage presumably will negate any savings.

Do the math. Say premium is 10 cents per gallon higher over mid grade. The loss in mileage is 1 mpg. The fuel used is 16 gallons. You have saved $1.60($0.10*16). You have lost 16 miles(1*16). At 23 mpg you need 0.7 gallons(16/23) to make up the loss in mileage. At $3 per gallon it costs you $2.10($3*0.7) in the loss of mileage of 1 MPG! Since you saved $1.60, your loss is $0.50($1.60-$2.10). :eek:

OK, experiment. See what YOUR numbers are and substitute in the above calculations.

IMHO, buy premium, religously check your tire pressures and maintain/drive the car for optimum fuel efficiency. ;)
 
RE: Using mid-grade gas

In the past, when i tried mid-grade i noticed a slight loss in fuel economy, at least enough to offset the difference in cost. But that was a long time ago, i think with my '94.

The ECU will only retard the timing so much based on the knock sensors. It's possible to get more knock than they can adjust for, depending on the vehicle. Deposits in the engine, lower grade fuel, high temperatures, and the wrong chip or MAF can all cause pinging.
 
RE: Using mid-grade gas

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... The ECU will only retard the timing so much based on the knock sensors. It's possible to get more knock than they can adjust for, depending on the vehicle. Deposits in the engine, lower grade fuel, high temperatures, and the wrong chip or MAF can all cause pinging.
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Makes sense.

Couldn't the Octane Adjust plug could be pulled to force timing back?
 
RE: Using mid-grade gas

When I purchased our '97 LSC about 3 years ago, the LM Used Car people had used it for about 2 years as a "pickup" car. They drive all over creation to go bring back purchased used cars to their lot. They told me when I bought the car that in all that time, ONLY regular gas had been used in the car. If you notice, that the decal on the cap cover and on the gas gague says "Premimum RECOMMENDED", not required. Manager at the dealership said I'm only increasing the profits of the gas company by putting preminum in it. I have been lining the pockets of the gas stations ever since....EXCEPT for the last few trips to the station...using regular. Made a trip to upstate NY with it and noticed absolutely NO difference in proformance nor milage than before. I fuel up at the same stations on the way up and back and take about the same amount as before. I think I'll stay with regular from now on......that knock retarder works REAL well in my Mark!!

Bud Pytko
'97 LSC Silver Frost
'05 F250 SD CC PSD 4 X 4 AZ Beige
'94 Prowler 5th Wheel
http://myfilelocker.comcast.net/charlespytko/Lincoln/BudPytko97LSC.JPG
 
RE: Using mid-grade gas

According to http://www.baileycar.com/gasoline_html.html :
The results were more dramatic with the test cars that require premium fuel. The turbocharged Saab's
sophisticated Trionic engine-control system dialed the power back 9.8 percent on regular gas, and
performance dropped 10.1 percent at the track. Burning regular in our BMW M3 diminished track
performance by 6.6 percent, but neither the BMW nor the Saab suffered any drivability problems while
burning regular unleaded fuel. Unfortunately, the M3's sophisticated electronics made it impossible to test
the car on the dyno (see caption at top).

Our tests confirm that for most cars there is no compelling reason to buy more expensive fuel than the
factory recommends, as any performance gain realized will surely be far less than the percentage hike in
price.

Cheapskates burning regular in cars designed to run on premium fuel can expect to trim performance by
about the same percent they save at the pump. If the car is sufficiently new and sophisticated, it may not
suffer any ill effects, but all such skinflints should be ready to switch back to premium at the first sign of
knock or other drivability woes. And finally, if a car calibrated for regular fuel begins to knock on anything
less than premium or midgrade, owners should invest in a tuneup, emissions-control-system repair, or
detergent additives to solve, rather than bandage, the root problem. Class dismissed.


http://www.usatoday.com/money/autos/2003-07-30-premiumgas_x.htm
Engines designed for regular fuel don't improve on premium and sometimes run worse. And today's engines designed for premium run fine on regular, too, their makers say, though power declines slightly. (Background: About Octane ratings)

But premium lovers are passionate. "I would simply curtail driving rather than switch grades," says Bill Teater of Mount Vernon, Ohio, who puts high-test in both his Cadillacs, though only one recommends it. He's sure both the DeVille and the Escalade run rough and lack pep on regular.

Prejudice and preference aside, engineers, scientists and the federal government say there's little need for premium.

http://members.shaw.ca/costall/1000Q/answers-gasoline.htm
If the ECU detects excessive, continuous knock via the knock sensor, the engine timing is retarded until the knock goes away. This results in a power loss, but saves the engine from damage. So, if you fill up with 87 octane gas, your ECU will be forced to retard the timing quite a bit, and you will not get the rated power from the engine.

http://www.chron.com/cs/CDA/ssistory.mpl/special/energycrisis/gasoline/2593995
But changing to an octane rating below the manufacturer's suggestion could harm your car, says Andrew Barron, professor of chemistry and materialscq science at Rice University.

(Don't know what you need? Go to your glove compartment, dig all the way to the bottom and look in the manual. Or call a dealer.)

The octane level reflects how much the gasoline can resist engine "knock," a knocking or pinging sound that occurs from premature, uncontrolled combustion, says Jim Williams, senior manager at the American Petroleum Institute, an oil and natural gas trade association. Over time, engine knock can damage various engine parts such as the piston.

Also, if you use a lower grade on a car that requires higher, do you invalidate your warranty?

Toyota and Tommie Vaughn Ford say it won't, Honda says probably not, Nissan says it depends on various factors and cannot be answered in a general manner.

http://www.washingtonpost.com/wp-dyn/content/article/2005/08/05/AR2005080501595_pf.html
Automotive experts say using regular gas in most vehicles does no damage and makes no discernible difference in performance. Cars made in the past 15 years have such highly refined computer controls that the engine will adjust to the grade of octane in the gasoline, even in cars sold as requiring premium gasoline. Some drivers -- in some cars under some driving conditions -- may notice a drop in horsepower, but for most people behind the wheel, it wouldn't be enough to notice, the experts say.
 
RE: Using mid-grade gas

All I have to say about this BEAT TO DEATH topic is. If you cheapskates want to use regular go ahead and save some lousy 10-15 cents per gallon and experience PROVEN (Many dyno tests proved lower performance in cars where premium was recommended) lower performance, gas mileage etc. Saving the same 10 cents that you spent when gas used to be $1 a gallon is not going to amount to any more savings now that you spend $3+ comparatively speaking you spent more on the difference before than you do now.
 
RE: Using mid-grade gas

We're also forgetting that using higher octane fuel results in a smoother running engine resulting in less carbon buildup and engine deposits. That alone is why I use premium.

As for rising fuel cost, I live in CA. My house payment is $2,600 a month. My wife's Hummer is $750 a month. I'll worry about fuel prices when they reach $10 a gallon.
 
RE: Using mid-grade gas

Obviously this is a subject with no clear answer. All the quotes in John's last post, however, do not mention anything about MPG, just some miniscule power loss. I've been doing a lot of reading the last few days and I find nothing really convincing that there is a mileage loss.

If the only loss is a small amount of power then I have no problem with that for daily around town driving. If I want performance I'll unplug my battery for 30 seconds to reset the ECU and fill up with premium.

As far as "cheapskates" are concerned, it's not being cheap, it's being pissed off! Someone sneezes and the price jumps. Local staions here went from $2.98 to $3.65 OVERNIGHT yesterday due to Katrina, even though strategic reserves are being released. So the point is, why put that extra $$ per gallon into the oil company's pocket when it can stay in yours?

Here's what I saved the other day with a 20 gal. fillup: Mid range @ $2.75 vs. $2.95 = $4.00 savings + 10% back uising Discover gas card = total saving of $5.50 Well now that may not be a LOT of money but hey, it's better in my pocket than the oil company's.
 
RE: Using mid-grade gas

I believe you'll find mileage variations model to model and car to car. I am a proponent of trying a lower grade gas and actually checking the mileage(not just by the message finder!) to see if it is a gain or loss! But as illustrated, a miniscle 1 MPG decrease clearly overshadows quite the price difference in the cost of premium over mid-range. IF you can truly justify the savings by doing the math, and do not miss the performance, by all means, buy the cheaper grade.

The flip side of this coin is if you have a vehicle that doesn't require premium(i.e. Lincoln Town Car 4.6L SOHC), you will most likely NOT gain any mileage nor performance by using a more premium grade of gasoline.
 
RE: Using mid-grade gas

I've noticed some cars advise "recommended" and others specify, "REQUIRED".

My LS bitches everywhere and says premium ONLY all over the place.

Oh well, just filled up for $3.10. I think it came out to $62? Or so ::wtf::

I got a 23gallon tank.
 
RE: Using mid-grade gas

If you don't want to feed the oil companies buy an electric car, or get a bicycle. Hell get a Prius or even Ford Escape Hybrid (if you want to stay on an American brand) if you can't live without a car. Cheaping out on those 10 cents will get you no where and it certainly won't "bite" into the profits of the oil companies/the oil barons of the Middle East.
 
RE: Using mid-grade gas

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"I'll worry about fuel prices when they reach $10 a gallon."....must be nice! Guess I live on the wrong side of the tracks....Bud Pytko'97 LSC Silver Frost'05 F250 SD CC PSD 4 X 4 AZ Beige'94 Prowler 5th Wheelhttp://myfilelocker.comcast.net/charlespytko/Lincoln/BudPytko97LSC.JPG
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Yeah, I married into money. My wife owns her own business.

Ergo, she drives the Hummer and I drive my $6,000 Mark.

Though I wouldn't trade for an instant!!! :)
 
RE: Using mid-grade gas

I've been a gearhead for more years than I care to admit to being alive. And there's one aspect of this dead horse I don't think anyone has beaten, and it's been nagging at me since the first thread I read posted on this subject.
It is true that a properly opeerating modern, computer controlled engine has knock sensors that will retard the ignition timing, and in most cases, will stop audible detonation and you probably will never feel the loss of power in normal driving. So it should be OK in a pinch when the premium is unavailable. But extended use brings on another aspect:
Retarded ignition can/will foster elevated exhaust gas temperarure (EGT). High EGT will subject engine internals to temps which may be above the design limits. This is especially true of exhaust valves.
Friend of mine (also co-worker till we retired) bought one of the small busses we all see around airports, used as a courtesy van for nearby hotels, rental car companies, and off site parking lots/garages. His intent was to convert to small RV, and since he only lived about 10 miles away, also used it to drive to work.
Engine was 440 cid MOPAR, which he had rebuilt.
In the mornings coming thru the large parking lot, I often heard/saw him drive in. Kept telling him it sounded like timing was retarded, plus he had lots of trouble burning up plug wires, had to use the Jacobs ceramic boots to stop them from burning, silicon wires burnt up!
Eventually the engine started losing compression and misfiring under load. Testing revealed severe exhaust valve burning and valve seat recession, requiring head removal and extensive rework of valves and seats.
Examining the distributor revealed faulty advance mechanism which had resulted in retarded spark timing and high EGT.
SO, IMHO, it is short sighted indeed to operate any high compression engine on fuel of a lower octane than recommend by the factory on an extended basis. Me, I'm starting to look around for a lightweight motorcycle, 175/250 cc, and a cargo basket for the back.
Sorry about the novel, but I felt this is important enough to warrant a full explanation of my concern.
 
RE: Using mid-grade gas

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SO, IMHO, it is short sighted indeed to operate any high compression engine on fuel of a lower octane than recommend by the factory on an extended basis.
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Very well put.
 
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