True. I dont generate lotsa boost. If i was that type of driver I would use 94. If I was going to race or run from the cops ..94, if i wanted to go 155mph, again 94. Heat, high loads, etc, 94 all the way. But with the vacuum gauge at -10, no need, gettin 40mpg at 55. If i'm in texas, ill bring a tank of 94. We can check out the upper limits of the speedo....together.

 

actually we have a gas station that sells 104 octane, of course it`s like $7-8 a gallon, would love to see what that would do

 

Higher octane is required for best performance and economy. In the old days before computer controls it would destroy an engine to run it if it did not have high enough octane. Now with todays computer control systems what it does is retards the ignition, downshifts into a lower gear and may even add additional fuel to protect motor. This hurts mileage and performance but saves the motor and definatly increases life of engine.
Todays computer control systems are very good. They sense detonation and make changes to protect motor in split seconds. They allow the car to have higher compression, boost and better horsepower for better mileage and performance. All of the variables the computer control have a huge effect on performance, mileage and durability of the motor. Plus they save you moeny every day. We used to have to change points, plugs and plug wires every 5000 miles or less. Now they last for 100,000 miles.

When the highest octane is needed most is when the motor is under a high load, low RPM pull (lugging the motor) such as getting on the highway in top gear at low RPM.
In those situations higher octane will definatly help your performance and mileage. If your motor requires 93 octane in those situations then 104 would not give you any more performance or mileage. But it does give you a larger safety margin. So you are completly right that if your motor does not need the octane it is a waste of money but if it does need it then it is a waste of performance and mileage atleast at the times it is needed. Your car may only need the higher octane 2% of the time and the computer can compensate for that so it may be better for you to use the cheaper gas.
Your decision based on your needs from the vehicle and budget.

 

The computer in your cars does many things most are not aware of. Most are somewhat rich because it is always better for a motor to run rich than lean as far as performance and durability. Lean motor detonates and hurts parts if not controlled by computer which hurts performance and mileage. Most monitor the engine temp and if you lose a water hose or something it will actually dump huge amounts of fuel and retard the ignition (safe mode?) to allow you to make it to a service facility. Gas mileage may be 4 MPG (wild guess) and top speed may be 35 MPH but it can get you to safety.

The computer control system also has to allow for a certain percent of variance on the sensors and there are many on these cars. If one of the sensors is off 3% then that will effect performance and mileage. Once again the factories will choose rich over lean to be safe. This is also one of the reasons some cars will perform and get better mileage than others.
There definatly is some mileage and performance gains in the computer control or tune. Todays cars are soo much better in so many ways than long ago but there are still improvements that can be made.

 

This is common sense curly1 (above quotes).

My father force fed all this stuf to me (lifetime auto mechanic by trade) when I was 9-12 years old. We didnt throw baseballs we changed head gaskets and timed engines on sundays.

To be honest he is the one that taught me to drive stick, and made it important to know how to drive for mileage

The uncommon part is my mpg. He saids the same things that you say, xxl and many other.

The point where may dad stops the conversation,is when his thoughts and the REALITY meet ,and don't line up.

He looked at me like I was in an idiot when I said i would be willing to put 87 in a "turbo engine".

One day he wanted to drive my hhr ss (a car which he also thought i was an idiot to buy)..were talkin drag racing rear wheel drive only v8 man, don't park your foregin ^&%& in my sight GM retiree.

Two things he learned real quick.

My hhr is sweet, and im sure that pride felt good goin down. (which is why he wanted to drive it...lol). The convertible corvette was probably offended sitting in the garage.

Second, that when he got into my hhr and turned the key, the dic was up on avg mpg.....and the 35.6 staring him in the face was priceless. I said nothing. He (drinks a little.....well not so little) said "you've been getting THAT kinda mileage" expeletives deleted...lol .... I said well that is only over the last 350 miles, You told me to only run high-test so i'll get 94 as soon as this tank of 87 runs out :)

When he brougth it back after les than 50 miles it read 31.3....lol

The only way the quotespeople keep posting here matter is if they can prove it. So the challenge still stands, if you want me to eat my words and pride, you better get 37mpg overall or better. Otherwise your just pissin in the wind.

Cleveland HHR SS 36mpg 517 miles on 14.4 gallons = 1
Haters, octane this, knock sensor that= 0

Better step up.


Oh a third thing my dad learned

His chemical engineer son is no idiot :)

 

He passed away in 1993 but I think he would like my HHR. It is a sporty looking economy car that actually runs decent for what it is.

Your Dad is probably impressed with your mileage, I am. It is better than my mileage. From your DIC when he brought it back he probably was impressed with performance to. He may have had his foot in it some.....

 

My dads foot lives on the floor of whatever vehicle he drives :) I think he got the bug back in '69 with his 302 z28, the first new car he ever bought. I can hear him saying it now.... Huggar orange , and ivory interior...lol, 4 inch bore three inch stroke 7000rpm. Take em third on the top end.
later

 

My mother-in-laws car has the instant MPG feature which I think is what you're looking for. However, for those of us who don't have that, try resetting the ECON while you're moving at various speeds on level ground. It would also help to maintain a conservative amount of pressure on the gas pedal while you're doing this. I haven't actually done this yet but I am willing to bet that your best fuel economy is going to be in the 40 MPH area on level ground.

It makes sense to me that fuel efficiency is like an arch. In other words it's going to start out low (like from a stop) because it takes more energy to get all that weight moving from a stopped position. Once you're moving you're going to peak out at a certain speed (again assuming level ground) and once you exceed that speed the efficiency is going to go down again. If you drew this out on a graph it should look like an arch. This concept is supported by lower city averages universally among automobiles (except hybrids) and Newton's law of motion when referring to the need for double the energy to increase speed by another half as much as you approach the speed of light (or try to anyway).

I don't claim to know exactly what I'm talking about but I think I'm making sense. LOL Anyway, I'm going to try exactly what I suggested and post the results at some point in the near future. I've been averaging 28 lately and the only change I've made is accelerating gingerly from stops. It takes a little longer to get up to speed but you'll still get there and to hell with the people behind me!

Regardless, good luck.

 

I have and can do better than 40mpg, however i will need to slow the flow of traffic. i don't do that when i hypermile. I hypermile so that only the people who think that a 35mph zone is a race get annoyed that I accelerate slowly. Most people never notice what i'm doing. i took a trip last weekend from akron-canton ariport to a mohican campground in ohio. 37.3mpg and I was able to stay infront of semi's on the open road in the slowlane..avg mpg in the overall was probably 65ish maybe 63....posted limit was 65 for cars 55 for semi's. No turning off the car at stop lights...and the area near mohican is a serious rollercoaster of a road, not flat at all...lol.

You need to do many things, time the rollers, keep the clutch to the floor whenever possible, never go so fast as to need braking for a stop, or light (youll need some, but try to limit how much). Coast the uphills down to 60ish, make up time on the downs.

The HHR SS can easily get 37mpg on the open road once warmed up with an attentive driver. 39-40 in favorable conditions/terrain.

I use third gear a few times to pass on a two lane highway, I could pass 3-6 cars at a time!!!!!! Without worrying that the on-coming opposite lane (the one I was in) would cause me to re-enter MY lane.

 

I bet you could better your economy by removing the spare tire, floor mats and everything else not bolted down like the owners manual etc. Oh and use the washroom before you leave! Probably be pushin 45-50mpg.