My Lincoln Mark, both the old one and the current one, are equipped with knock sensors and the owners manual states to always used 91 or better gasoline.
Performance and fuel economy is the same no matter what octane is used. From 85 to 91 it’s the same, other than the slight improvement at higher altitudes.
Even at near a quarter million miles there has never been a problem and the main arbiter of this, the spark plugs, never lie.
The problem with the Cadillac story is not the choice of lower octane fuel; it’s the loose nut behind the wheel who obviously chose to turn the volume up on the stereo as to drown out the severe pre-ignition rattle that was occurring while he was forcing a turbocharged vehicle up a mountain grade.
If we can afford the $30,000 car, we should be able to afford the higher priced fuel if it is recommended. But then there are those who can’t afford the car or the fuel. Maybe we should shop for fuel like we shop for cars. We don’t all want the cheapest cars.
With the advent of electronic engine controls and direct injection. Compression ratios don’t mean much anymore. The 3.7L in the upcoming 2011 Mustang V6 has a compression ratio of 10.5:1 and it’s spec’d for 87 octane. Even the 3.5L V6 in the new SHO has 10.0:1 compression and two turbochargers and it will run on 87 octane as well. The 3.6L V6 in the CTS has a lofty 11.4:1 compression ratio and only calls for regular unleaded. The game has changed.
Well, several people don’t really “own” the vehicle, they’re just rent…er leasing the vehicle, so they can’t really “afford” the vehicle they’re driving.
Just be glad that your vehicles don’t require 110 octane. Just checked the pump at the station here that carries it. $6.29 a gallon. 87 was $2.85, 89 was 2.95, 93 $3.05. do THAT math.
I’m sure there are cars that don’t improve - same with my ES300. Premium is ‘recommended’, but I get same mpgs and performance with regular. I would just expect more ‘premium required’ cars to show a difference. But not all.
If “Regular” was 87 octane and “Premium” was 100 octane, all these arguments would have some validity… There would be a good REASON to use premium fuel if required. But that is simply not the case…
Most engines designed to run on 91 octane fuel will tolerate 87 octane fuel without any problems. They do it every day…
I sure have. Back when I sold Fords I wittnessed a guy in the midst of throwing a temper tantrum in the service dept because he was denied warranty coverage for an engine repair. He was using regular in an 02 Lightning pickup, a vehicle that requires 91 octane or better.
Some years back, I set the timing a little too far advanced on my 1971 Ford Maverick with a 250 cubic inch 6 cylinder engine. I set off on a road trip and even under moderate acceleration, I was getting spark knock. I took it easy on the accelerator until the gasoline tank needed to be refilled and I refilled with premium gasoline. The spark knock disappeared and the gasoline mileage really increased. The acceleration also improved. Now I know that modern cars have a microprocessor that sets the ignition timing, but if a car calls for premium, wouldn’t it make a difference in the gasoline mileage because the microprocessor would allow more spark advance? I continued to run premium in the Maverick until I tuned up the engine again and set the timing a couple degrees less advanced.
I’m sure in some cases the computer can take advantage of the premium. I’ve heard folks with BMWs, Infinitis, Subaru turbos, and Ford itself (on its new Mustang V8) report better mpgs, performance, or both with premium. Others (my Toyota/Lexus v6, for example), no difference.
I have another related question: I am about to inherit a 10 year old Acura. It has only used premium gas. Assuming premium is not required per the manual, would suddenly supplying this vehicle with regular gas cause damage or stress to the engine?
I too have noticed the big jump in gas mileage in the mountains of Colorado. You can get away with 85 octane fuel up there because the air’s less dense, which effectively lowers the compression of the engine. I assume the gas mileage gains come from the engine’s electronics sensing the thinner air and leaning the mixture. Of course a side effect is slightly diminished performance…
Best Case Scenario using Regular instead of the recommended High-Test.
The anit-knock sensor kicks in and backs the timing off which will cause the car to get worse performance and worse gas mileage then using the recommended high-test.
The WORSE case scenario:
The knock sensor may malfunction and it WON’T back the timing off…thus causing the severly knock and blowing a hole in one or more of your pistons.
It seems to me that if we, as Americans, stopped buying cars that “require” premium, carmakers would stop building them. Another way to squeeze money out of us. But then again, I guess that’s why I’m Mr. Cheap. I know if I was shopping for a vehicle, that would be a dealbreaker for me. Turns out, ya gotta ask a lot of questions when buying a car. Like stories I’ve heard about people buying a car that requires REALLY EXPEN$IVE TIRES, and they don’t realize it until it is time to buy new ones. <:-)
I agree, but unfortunately most automotive purchases are emotion-driven rather than information-driven. The realization that it’s going to cost extra to run usually follows the purchase.
And there’s other motivations. I chose my car because the manufacturer was known for reliablity, my experience was consistant with that reputation, and it was REALLY comfortable for my really nbad back. I didn;t realize that it took really expensive tires. But my back doesn’t care. I’d repeat the same choice again if I had it to do over knowing what I know now.
Audi 2.ltr in VW van. I used 87 and a few times 89 with no better MPG. Then I put in 91 and now get 23-24 MPG ( at 6,000 ft.even) while before I got 18-20. Manual says use highest octane available. 10:1 compression ratio.
I figured $.02 extra per mile using 91. Better for engine at least.
Exactly how many points are required to cause damage?
You are making broad comments. Are you willing to pay for damage if someone follows your advice?
How do you feel about the true cost difference? If premium is required or recommended, and regular is used, likely milage will be reduced, is the lower cost per gallon on fuel enough to recover the additional cost of using more fuel?
Why would the auto manufacturer state that premium was required or recommended if there was no reason to do so? Are they trying to sell more cars by telling potential buyers that they are going to have to buy more expensive fuel?
