Modern cars usually are rated with max horsepower using premium fuel, usually 93 Octane. Most of them run fine on 87 but produce less horsepower with the lower octane. How much power is lost?

My Taurus SHO 365 HP with premium but how much using 87?

Comments, facts, good guesses appreciated. Thanks, Robert

 

OK...I'l bite..

Here are some tid-Bits to chew on...No guessing here...Actuallity...

You will actually lose HP by running a higher octane fuel than what the engine was designed for. You can also damage your engine by running a lower octane fuel than what your engine was designed for.

Your SHO's engine is a low compression engine designed to run the high octane due to its use of turbo chargers which increases it overall compression ratio. The high octain fuel required is used to eliminate pre-ignition, A.K.A. "PING" or "SPONTANEOUS COMBUSTION".

Low octane fuels are more volatile than high octane fuels. So, if you run a high octane fuel in a low compressioned engine, you will lose HP as the fuel will ignite and form the required flame front too late in the timing sequence, thus a loss in HP and MPG.

Running a low octane fuel in a high compressioned engine, you run more of a chance for the fuel to ignite on it's own thru compression (spontaneous ignition). Turbo charged engines are even more prone to this as the intake air gets heated while being compressed (hence the use of intercoolers). The results are detrimental. Hopefully, the knock sensors (if the MFG uses them) pick the pinging up and retards the timing to eliminate any potental damage. The retarding of the timing results in a loss of HP and MPG.

Unless the MFG's changed their ways, which I doubt. The MFG HP ratings for any engine is derived by running the engine on a DYNO with no accessories attatched to the engine. This includes no water pump, alternator, A/C compressor, P/S pump.

 

Thanks for the intro to IC Engineering 101. On several forums I posted the same simple question about HOW MUCH degradation would occur. I naively hoped maybe someone would cite dyno or test bed results, etc.

It seems to have awakened some latent urge in people to lecture around the subject rather than address it. Yours was one of the better and to-its-point responses. My posting in gunbroker.com 'general' ran on to 25+ replies some as much as 4x the length of yours.

That said, I probably should have said that I started my technical life as an A&P licensed/trained airplane mechanic. Eventually I scrambled up the ranks to VP level in charge of a world-wide operation of 7000 'motorized units', a member of SAE for 15 years sometimes on their working groups.

This thread brought to mind that Ford has really gone into the fuel saving tack employed by Lindbergh in the So Pac during the war. Flying a P-38 he was returning from missions with a lot more fuel than the Army pilots on the same mission. He did low RPM with high manifold pressure (coarse pitch prop & more throttle). On wife's Lincoln MKS I have got 28 mpg at 75 mph on highway trips. Not bad for a 4600 lb car. Along with its solid fuel injection, dual turbos, 6 speed trans, its low number rear gives around 1600 rpm at 75 mph - all with a little bitty 3.5 liter mill.

I'm in a Don Quixote 'quest for the truth'. I have a few emails out to old-time high-tech minded car buffs, people who have also been there and done that. When I get results I will post it here.

Horrors - it must be contagious. I have a case of keyboard diarrhea myself.

Seriously, Thanks, Robert

 

Time for my keyboard to ramble...

I usually find it better to leave out what ones background is. Otherwise, you can get the "well, if you're a mechanical engineer, why are you asking such a question?". Or "If you're a chemical engineer, why are you asking if synthetics are better than petrolium lubricants".

Anyways, since the MFGs have lots o' dollars, they can do more than the average Joe like us can. As long as they can prove it, they can publish it. With that said, I would suspect that they use the same fuel for HP/Torque testing that they use for MPG testing. A perfect 8 carbon molucule chain. They pay extra for this "PERFECT" fuel, while we as consumers get a fuel that can range from 7-11 carbon molecule chains. The MFG's can also control the air temperature, engine temerature, ambient air pressure, humidity and such to get the "PERFECT WORLD" for testing. We are stuck with 100% of all other variable configurations in the real world.

The MFGs also in the end I suspect, program the vehicles to a "SAFE" zone for their own comfort of not needing to pay out for warranty claims and brand related failures.

An example would be like...If I built engines and gave a 5 year/100,000 mile waranty, I would de-tune the engine just a touch as not to allow it to reach it's full potential.

Now-a-days, engine management programming goes a long way. We just recently traded in our 2008 Sable with the N/A 3.5L engine. It would average 30-32MPG on the highway up to about 75MPH, then would drop to the 28MPG range when you would run 80-85MPH.

We now have a 2010 Lincoln MKZ AWD and I'm curious to see how that averages out. It's a smaller car with the same engine/tranny, but ofset by the AWD. It's only been on the highway twice and just past the 1,000 mile mark.

I'll stop for now to see if there are any other peeps out there.

 

I went to my Ford salesman (for past 15 years) for delivery update of my SHO, told him my story. He called his Ford power guru, who responded "about 5% loss 87 from premium max, more maybe 8% loss using ethanol" - quick response with no discussion. I'm still looking for other info hopefully from dyno or testbed. At least I now have a number.

So what else is new?? Another 'anecdote" reports a trip of 900 miles using basic unlead one direction and premium return. Got same MPG both ways, with only difference noted premium better accelleration when passing. I think driving an Acura TL.

To be continued ---------->

I see you are into lubricants - more anecdotes. Back in prehistory when I was simulating work, one of the super execs would ask if synthetics would really make his engine last longer. Yes. Did I use it? No. Why not? The mfg recco lubes will make my engine last longer than I will have it and I'm not trying to benefit the third or fourth owners. --- Do we use synthetics in company vehicles? No, because engine life is not the issue in that our 'employee demolition derby' and lack of maintenance take care of that.

 

I doubt you'll ever get real numbers in regards to HP/Torque output using different fuels. The loss using 87 octane and the higher loss using ethanol makes perfect sense. The computer will detune the engine due to the "KNOCK" issue and ethanol fuel can have a phase seperation that will cause a 2-4 point decrease in octane causing the higher loss in HP/Torque.

On the subject of lubricants, I use the AMSOIL as a personal preference and the fact that I normally keep everything for about a zillion years. Like my 30 year old 10HP Gilson snow blower that uses no oil and starts on the first pull. AMSOIL is my choice in this catagory.

Mosh companies that have fleet vehicles are pushing the "GREEN" issue, but still use DINO juice. Reason being is that the DINO juice is a lower price and gets changed more frequently (our company policy is every 5,000 miles). This forces the driver to take the vehicle into the specified/authorized service centers for the oil change and a vehicle inspection for brakes, tire wear and such before major issues arise. The use of a synthetic doesn't guarantee an increase in oil servicability unless the oil MFG specifies it like AMSOIL (Who I believe is the only one).

Also, the mathmatics work well for me. With even a 5% increase in fuel mileage using the AMSOIL, the money saved on fuel costs offsets the cost of the yearly AMSOIL fill for my toys. So basically it's like getting my yearly AMSOIL change for free. And it's cheap insurance for the reduction in component failures.

Where were we? Oh yeah, HP. I was looking at our new Lincoln and cannot see for the life of me how the engine can even breath the way the intake area is blocked off so much. I'll need to modify that area so that it can get more free flowing air into the air box. This will help increase its overall HP output. Not a lot, but something is better than nothing.

You're turn...

 

Nobody really needs the info I want. Altho someone probably has it as a by-product of something else, nobody is likely to hear about it. Like some human ailments that never kill anybody. Not enough interest to research a cure. I'll probably hear a new set of number eventually.

As for automotive dog and pony stories, mine are few and certainly nothing modern. I have changed cars every few years since I retired in '80. Before that the nearest thing to an adventure was owning an Olds diesel. I got it during the fuel shortage when I was living in NY and it worked OK for me. I put a furnace oil tank in my garage and had our furnace oil delivery keep me in fuel. With all the horror stories about them I kept holding my breath it would twinkle out on me but never did. I traded it at about 40k miles after I moved back to OK. Right now I'm driving a '09 Nissan Murano with the shiftless trans. It is the only car I have ever had that I didn't become dissatisfied about something it did or wouldn't do. Its days are numbered because my wife has engineered a deal that our son should have it and I something new. I ordered the SHO due now 10/25. My '06 Mustang GT went that way to our daughter and I got the Murano. My wife would drive anything forever but wants everyone else to ride in style. Not that she is suffering with her Ecoboost Lincoln - but she will drive it from now on or until it won't do what she wants it to do.

Here is one of my prehistoric automotive events from my memoir.

RUNNING MY CAR ON KEROSENE DURING WW2

A little preamble to set the perspective - I worked for Pan American Airways which operated like a US Navy transport squadron. Pan Am had pioneered Pacific aviation before the war with bases it had established for its operation. We employees were in the US Navy on inactive duty (from which I got an Honorable Discharge after the war). Pan Am entered the war with four 4 engine flying boats, to which the Navy added 15 4 engine and 7 2 engine aircraft. Our official name was NATS, Naval Air Transport Service.

Returning to San Francisco after a year in Hawaii, the only transportation I could buy was a motorcycle. Almost constant cold wet weather demanded something better. I saw this 1924 Studebaker outside a junkie with grass grown around it. It looked good, inquiry found it held up in an estate probably to be junked. Couple weeks later I got a post card he could sell it. For $35 I got my obsolete car in great condition, with 8 ply tires and two spares. The downside was it was a real gas hog - tragic for me because of wartime gas rationing.

My two gallons a week gas ration was barely enough for my motorcycle. I had heard about running Fordson tractors on kerosene. Being an experienced airplane mechanic I figured I could make this car go with kerosene. Studebaker couldn't be much different from the Fordson tractor. I had no information how to do it so it was start at square one.

Apparently in 1924 gasoline required a lot of coaxing to make it
burn properly in cold weather. The primitive design of the old
car was such that it had heaters that could pass the carburetor
intake air over the hot exhaust pipe plus a means of warming the
fuel-air mixture between the carburetor and the engine. It had to
be able to run on kerosene and I would figure out how to do it.

The owner of the car wrecking yard where I bought the car got
interested in my project and happy to help. Back to his place and
bought a Ford Model T carburetor and intake manifold. I bored
a hole in the Studebaker intake manifold, cut the mount flange off
the Ford manifold and had it welded on the Stude manifold. This
permitted having two carburetors, gas and kero. Made a one gallon
tank from a hydraulic oil can and rigged controls so the small tank
and Model T carburetor ran on gasoline. Kerosene went into the
original Studebaker gas tank and fuel system. The result was better
than I had dared hope for.

The only restriction was that it required that the engine be
warmed up good to run well on kerosene. It was about three
blocks from where I lived to get on the highway to work. I started
and ran on gasoline the first few minutes, then start cutting in
the kerosene and reducing the gasoline. This was done with the
accelerator and throttle controls. By the time I had gone about
half mile I was on kerosene only. At highway speeds it ran as
well on kerosene as it did on gasoline. When I went into San
Francisco, I had to cut in more of the gasoline because the
engine lost heat at slow city traffic speeds.

Kerosene cost ten cents a gallon and was ration free. I had all
the gas I needed for both the car and my motorcycle. I drove the
old Studebaker for almost a year until I transferred to New York
in 1945. I then sold it for what I paid for it, $35.

One day in San Francisco going down a real steep grade I had put it into second gear rather than rely on its rear two-wheel brakes. Good that I did but the engine over reved and broke an exhaust valve. I chugged on about 20 miles home and pulled the head. Two learning experiences. No carbon build up in the engine. A rag wiped the pistons clean so you could see the numbers on the. The valve was made with a cast head brazed to its steel stem. The man where I bought the old Stude, told me to go back into a bin and find a valve big enough in head and stem diameter and longer than the original. He reworked the keeper end and I was rolling again.

Have a good one!! Robert

 

Nice read...Sounds like something my father would have done, probably did and hasn't gotten to story yet...

 

Very interesting you brought up how horsepower was originally done in the lab with no accessories or pumps, steering ect. That is 100% true especially during the 50s and 60s for muscle cars. That’s why if you have a classic car from around then and you dyno tested it the BHP would be lower than what the manufacturer claimed when the cars were actually made. In fact to your last statement about modern cars being that way unless car companies have changed their ways they actually have for once ! Not sure if anyone watches/listens to the Carmudgens Podcast with Jason Cammisa and Derick tan-Scott (which if you don’t y’all should on YouTube it’s absolutely fantastic for car nerds) but they actually talked about this in the new corvette episode I believe. Car manufacturers actually do horsepower ratings with everything attached to the point that’s it’s pretty close to the way it will be bought. I’m sure they don’t turn on the air conditioner and little tricks like that but manufacturers actually are required I believe to do it this way now just as an answer to your last question.

Also as a 2015 Taurus SHO owner this question about BHP difference is something I’ve been trying to figure out for years. With most cars this wouldn’t be true but the SHO is different in a sense that the computer will sense a higher octane and change (atleast I think That’s what I read lol) the owners manual does actually say there is a “performance loss” with regular unleaded but it’s totally safe to use. I would love to test this officially on a dyno one day but it would be an expensive way to find out a small question and I’ve seen different answers all the time in this question by everyone from Racers, Engineers, mechanics to petrol heads so maybe the dyno way would be great to get a clear cut answer!

 

Octane is a measure of resistance of a fuel to pre-ignition and nothing more. If an engine is designed to operate on 87 octane RATED gasoline then putting 93 octane RATED gas in the tank changes absolutely nothing. It is only when an engine is designed for high octane RATED fuel is there an effect.

For any car or truck produced in the past 20+ years that is designed for 93 octane RATED gas if the owner puts 87 octane RATED gas in the fuel tank the effect is that the engine's computer will automatically RETARD the point of ignition to minimize pre-ignition and protect the engine. With a retarded point of ignition the engine will produce less horsepower and the vehicle will go less distance on a gallon of fuel.

But Octane Rating or knock resistance is not linear. Mix 5 gallons of 93 octane rated gas with 5 gallons of 87 octane rated gas the end result is not a 90 octane rating but something closer to 91-92 octane rated fuel. When engineers spec 93 octane rated fuel it is with the knowledge that this fuel is readily available. They are not going to specify 90 octane as it is not something found at the pumps and there would be a lot of confused motorists at the pumps.

It has been this way for more than a century and the only thing that has changed is the advent of electronic ignition systems that detect pre-ignition and automatically adjust the amount of spark advance. What made a tremendous difference was eliminating tetraethllead from gasoline which eliminated the primary source of mental retardation with children and greatly extended the longevity of auto engines. 40 years ago an owner with more than 100,000 miles on the odometer was delighted but now it is routine to put 200,000 miles on a gas engine and with the Toyota they have a club for people with 200,000 or more miles on their truck and quite a few people have more than 300,000 miles with the orginal engine.

General Motors knew that tetraethllead shortened engine life but they owned the patent on the fuel additive and if engines did not last as long that was good for business as well.