Interesting... 2 octane, 5MPG

[E.B. Cornburner]

I wonder if the SOHC engines have knock sensors, that 4.0 has a good compression ratio.

Well according to Ma Bell and Carquest, both model years that I asked about, a '99 4.0L SOHC "E", and a '02 4.0L SOHC "K" FFV, show a knock sensor in their listings. The '99 4.0L OHV "X" doesn't list one though.

 

[CDW6212R]

I'll bet that was the Ford trend. As they built a high compression engine, they saw a need for the knock sensor. They just need to give us the option of a max power engine with the high compression, a tuned for power camshaft, and the premium gas.

I find it odd that the low compression engines have more power potential(supercharger), and the high compression engines are better for economy. This is why I chose the SOHC model I have.

 

[JohnnyO]

Most newer cars have knock sensors that detect detonation and retard the engine timing to protect the motor. If you use a fuel that has too low an octane rating, the computer will pull timing to prevent detonation and thus cause the motor performance to suffer since less timing means less power.

True, however a higher octane will let the computer advance the timing, if there is no knock, within the computer's "window"....which isn't a whole lot, absent a chip or XCal2 to advance it more. But using 89 may help a little bit.
That said, different parts of the country get different blends of gas at different times of the year. Where I live we get the crappy oxygenated gas in the summer (June 1 to Sept 15, the gas pumps say so) and my vehicles run better on 89. After September, I go back to 87.
As far as high-compression, my dad used to have a BMW with about a 10.5 or 11-to-1 ratio and it required premium fuel. When gas went way up he tried 87 but the mpg drop was enough that it was cheaper to run premium.
Maybe apples and oranges, but my two-stroke jetski says to use 89 if you have oxygenated fuel, otherwise 87 is okay.

I'll bet that was the Ford trend. As they built a high compression engine, they saw a need for the knock sensor.

I could be wrong, but I believe the first engine to use a knock sensor was the Buick 3.8L turbo, back around 1977 or so. The original Mustang SVO with a 2.3L turbo had a switch for regular or premium fuel.

 

[E.B. Cornburner]

I think the reason why your jetski requires 89 octane if you're running oxygenated fuel is because it leans the A/F ratio out slightly, and running leaner my increase the risk of detonation under heavy loads. The primary oxygenate used (maybe the only one now that MTBE is gone) is ethanol, and it will lean out the mixture somewhat due to the extra oxygen in it.

 

[JohnnyO]

Right, but wouldn't it effectively lean out the mixture in a four-stroke engine also? Alls I know is when I had my '99 Ranger with a 3.0 it would ping like crazy on the summer 87 gas, no matter how many trips back to the dealer to fix it. Had to run at least 89 in the summer, 92 was better when I could afford it.

 

[daprez1963]

Right, but wouldn't it effectively lean out the mixture in a four-stroke engine also? Alls I know is when I had my '99 Ranger with a 3.0 it would ping like crazy on the summer 87 gas, no matter how many trips back to the dealer to fix it. Had to run at least 89 in the summer, 92 was better when I could afford it.

i cant seem to understand this.

prem 92 runs usually 20cents more than 87. if i were almost empty, i would fill it up with 20 gallons. that would mean an extra $4 a tankfull. in my case, that translates to an extra $20 a month if i wanted to use prem gas. i see no need, but sometimes i prefer the higher octane in certain cars. if i am riding around in a SUV that uses 15mpg and can afford that, i am sure i can afford the extra $20 a month using prem, especially if 87 caused knocking. please dont think i am getting on you, but it kills me when people say they cant afford a certain gas so they buy reg 87.


everyone has the choice to use what they want, but if you really wanted to use prem gas, price shouldnt really matter.

 

[E.B. Cornburner]

Right, but wouldn't it effectively lean out the mixture in a four-stroke engine also? Alls I know is when I had my '99 Ranger with a 3.0 it would ping like crazy on the summer 87 gas, no matter how many trips back to the dealer to fix it. Had to run at least 89 in the summer, 92 was better when I could afford it.

Yes it would lean out a 4-stroke engine too. Remember too, that pinging on a certain octane is also produced by other variables, such as intake air temperature, engine coolant temperature, and since the PCM is seeing a higher IAT and possibly ECT value, the fuel mixture is leaned out compared to driving in cooler air.

In all reality, the winter gas with more light aromatics in theory should ping more than summer gas.

 

[JohnnyO]

In all reality, the winter gas with more light aromatics in theory should ping more than summer gas.

Well like I said, what gas you get when depends on where you live. Some places get the oxygenated gas in winter (like you), some places (like me) get it in the summer.

 

[E.B. Cornburner]

We're not mandated to have any oxygenated gasoline here at all. Only the counties around the greater Milwaukee area are required to have a reformulated (i.e. 10% ethanol) blend all year round.

But, the blend does change in accordance with the temperature. In the winter time, the suppliers add more isobutane and other lighter aromatics which help cold starting, but kill MPG. This is the case in any state that sees temperatures similar to ours.

 

[daprez1963]

We're not mandated to have any oxygenated gasoline here at all. Only the counties around the greater Milwaukee area are required to have a reformulated (i.e. 10% ethanol) blend all year round.

But, the blend does change in accordance with the temperature. In the winter time, the suppliers add more isobutane and other lighter aromatics which help cold starting, but kill MPG. This is the case in any state that sees temperatures similar to ours.

In arizona as well (not because of the cold since winters there are mild), the 10% ethanol is required by the government epa in those large cities because of smog emission. i think it runs from sept to april.

 

[E.B. Cornburner]

Yup. When I was out there, it was mostly MTBE, not ethanol used as the oxygenate. My car didn't really notice any difference, but it smelled funny out the tailpipe.

Since we're talking about knock sensors and stuff, I'm reminded of my last trip to Arizona. I filled up in Flagstaff, which has 85 octane regular unleaded, and still had gas leftover when I arrived in Phoenix. In the cooler weather and higher altitude, it ran fine. It was in the 60s in Flagstaff, but was 110s in Phoenix. Talk about ping city! I found a place nearby that had Unocal 76 Competition 100 unleaded race gas, and dumped a few gallons of that in to get my octane up. I still got pinging on 87 in Phoenix, so 89 was my octane of choice the whole time I was out there.

 

[daprez1963]

Yup. When I was out there, it was mostly MTBE, not ethanol used as the oxygenate. My car didn't really notice any difference, but it smelled funny out the tailpipe.

Since we're talking about knock sensors and stuff, I'm reminded of my last trip to Arizona. I filled up in Flagstaff, which has 85 octane regular unleaded, and still had gas leftover when I arrived in Phoenix. In the cooler weather and higher altitude, it ran fine. It was in the 60s in Flagstaff, but was 110s in Phoenix. Talk about ping city! I found a place nearby that had Unocal 76 Competition 100 unleaded race gas, and dumped a few gallons of that in to get my octane up. I still got pinging on 87 in Phoenix, so 89 was my octane of choice the whole time I was out there.

The AM/PM gas stations owned by ARCO used ethanol (10%) in their gas. There were several of these stations there and I used them almost exculsively. Their gas seem to run my cars better.

 

[daprez1963]

Cornburner. would you mind please telling me the lowest E85 price and where this station is...someone on another forum is disputing that E85 is that much cheaper than regular gas. they claim it is only 15% cheaper...thx

 

[E.B. Cornburner]

Cornburner. would you mind please telling me the lowest E85 price and where this station is...someone on another forum is disputing that E85 is that much cheaper than regular gas. they claim it is only 15% cheaper...thx

It varies depending on your area. There's a handful of stations in my area in WI called "Renew", and they're owned by the ethanol plant. They have the cheapest E-85 I've found. Check www.renewe85.com for locations.

Otherwise, www.e85fuel.com will give you a nationwide map of E-85 refueling stations.

Latest price check at Renew was $2.319 for E-85, compared to our regular unleaded at $3.149.

Other places tend to be about 15-30 cents per gallon cheaper than regular. I drove past a BP station that had E-85 for $2.999 compared to $3.199 for regular.

 

[daprez1963]

It varies depending on your area. There's a handful of stations in my area in WI called "Renew", and they're owned by the ethanol plant. They have the cheapest E-85 I've found. Check www.renewe85.com for locations.

Otherwise, www.e85fuel.com will give you a nationwide map of E-85 refueling stations.

Latest price check at Renew was $2.319 for E-85, compared to our regular unleaded at $3.149.

Other places tend to be about 15-30 cents per gallon cheaper than regular. I drove past a BP station that had E-85 for $2.999 compared to $3.199 for regular.

That Corn...

btw...i found this site that answered it too.... E85Prices.com

 

[irocdupi]

You have to watch to, I have an 03 V6 XLT and I quickly noticed the difference between the summer and winter gas. The gas that we use in the winter gets less MPG because it has more additives. Right now I am averaging about 12 strictly around town, and I know in the summer it jump up a little.

 

[thepotroast]

I think we're about 2.5 years late on this one :

 

[Joe Dirt]

Hey- it's all good, just means irocdupi is reading old posts- that's awesome!

 

[jseabolt]

I did an unoffical experiment on my Subaru Baja a couple of years ago. When I goto the beach I fill up at the house and top off at 3/4 of the trip or after 300 miles. I always average about 28 mpg.

The car was needing new tires so I decided to over inflate them from 30 to 45 PSI and topped off with a tank of 93.

The car gained an additional 3 mpg. The most I have ever got from this car.

My theory was the higher octane fuel would allow the engine management system to advance the ignition timing further. However under cruise an engine shouldn't knock anyway so that theory doesn't hold water.

I believe it was the higher tire pressure than made a difference.

Also I've noticed cars usually get better gas mileage in the summer versus winter. My theory on that one is reformulated gasoline. Now that they have started putting ethanol in gasoline, my 68 Fairlane and my 87 Yugo are really bad about hot starting in the summer. Well the Fairlane has always been hard to start when hot, only worse now.

One time I was running a tank of winter gas in my 68 Fairlane and had even been driving the car for several miles I pulled into the ATM and the engine started idling rough. Eventually the engine died and I couldn't get it restarted. I ended up running the battery down. When I pulled the hose off the mechanical fuel pump there was no fuel in it but I had over 1/2 a tank! An older gentleman who said he was a retired mechanic from the local Ford dealer stopped to help me and said the car was not making any spark.

I had the car towed home and started looking for the problem. By that time the engine and everything had cooled down and the car fired right up and ran fine ever since. So I have no idea what I did to fix it. The only thing I could find was a chaped wire inside the distributor going to my Pertronix Ignitor. I fixed it with heat shrink tubing and haven't had any issues but still don't know if it was lack of fuel or lack of spark.