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Best Fuel Tank MPG and Range to Date


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I've had the truck for a few weeks now and this past fuel tank has yeilded the best mpg and range to date. Previously I had only been averaging around 17.5mpg doing a mix of city and highway. However this past week yielded a very nice 20mpg. Now I will say this, this is the first time I've filled up on 91 octane. Before this week I'd only filled up on 87. Now, before I get yelled at, I understand how octane numbers work. If you tried to argue that your 2001 Honda Civic ran better on 91 vs 87 I would laugh at you. My question is, do these trucks adjust timing based the type of fuel it detects? My understanding is that it adjusts timing and flow levels based on a sensor which detects ethanol quantity in the fuel. Would this sensor also detect octane levels?

 

 

 

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So far this is my lifetime average mpg. I think it should be a bit higher but I tow frequently, and the one time I filled up on e85 really brought my average down.

 

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This is my previous 50 mile average and best for this fuel tank.

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The truck has no sensor to determine ethanol content. It plays with timing to calculate it. Because of that, higher octane fuel should kick it to an E85-like timing table to get a bit more power. Seeing a increase in MPG from higher octane is fairly common. You just need to sort out if it's worth it money-wise.

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The manual says that when you buy gas the computer has to make adjustments based on the type of gas you buy. Here it is from the manual if you have a 5.3. Most people don't know there is a 7 mile adjustment period for the computer to adjust to the fuel purchased.

Drive at least 11 km (7 mi)

immediately after refueling to allow

the vehicle to adapt to the change in

ethanol concentration.

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I recently hooked up my Scangauge 2 and have been monitoring timing and knock retard. Lately I have been trying to fill up with 89 octane but there has been a few tanks of 87. I have taking a few trips both unloaded and towing my boat (about 2500 pounds) while monitoring knock retard (KR) and timing. Here are my observations.

 

While unloaded, the engine gets more opportunity to go into V4 mode. While in V4 mode, timing is reduced quite a bit (anywhere from +4 to +12 degrees of total timing). I have seen quite a bit of KR while in V4 mode. Lets say the cruise is set and I'm in V4 mode with no KR and +6 degrees of timing advance. I'm about to approach a small hill. Once going up the hill, the engine needs more power and throttle position will increase (can monitor this also). This is when I will start getting KR (around 3-6 degrees) which of course retards the timing. If the load is too much this is when the engine will switch from V4 to V8. Once in V8 mode, there usually is no to very little KR with anywhere from 28 to 36 degrees of timing advance.

 

While towing, I usually see very little V4 mode unless I'm going down a hill. I have noticed KR in V8 mode while in the same situation I described previously (going up hill, throttle increases, KR shows up). Both of these scenarios are under light to moderate throttle increase conditions. I have yet to watch KR when under full throttle.

 

I'm no engine tuner by any means but from the observations I have seen with my Scangauge, the 5.3 develops quite a bit of KR and might possibly benefit from 91 octane. From what I have read, retarding timing reduces horsepower quite a bit and I can only assume MPGs would suffer also. I plan to use 91 octane for here on out and see if I see reduction in KR and how mileage compares with it.

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I recently hooked up my Scangauge 2 and have been monitoring timing and knock retard. Lately I have been trying to fill up with 89 octane but there has been a few tanks of 87. I have taking a few trips both unloaded and towing my boat (about 2500 pounds) while monitoring knock retard (KR) and timing. Here are my observations.

 

While unloaded, the engine gets more opportunity to go into V4 mode. While in V4 mode, timing is reduced quite a bit (anywhere from +4 to +12 degrees of total timing). I have seen quite a bit of KR while in V4 mode. Lets say the cruise is set and I'm in V4 mode with no KR and +6 degrees of timing advance. I'm about to approach a small hill. Once going up the hill, the engine needs more power and throttle position will increase (can monitor this also). This is when I will start getting KR (around 3-6 degrees) which of course retards the timing. If the load is too much this is when the engine will switch from V4 to V8. Once in V8 mode, there usually is no to very little KR with anywhere from 28 to 36 degrees of timing advance.

 

While towing, I usually see very little V4 mode unless I'm going down a hill. I have noticed KR in V8 mode while in the same situation I described previously (going up hill, throttle increases, KR shows up). Both of these scenarios are under light to moderate throttle increase conditions. I have yet to watch KR when under full throttle.

 

I'm no engine tuner by any means but from the observations I have seen with my Scangauge, the 5.3 develops quite a bit of KR and might possibly benefit from 91 octane. From what I have read, retarding timing reduces horsepower quite a bit and I can only assume MPGs would suffer also. I plan to use 91 octane for here on out and see if I see reduction in KR and how mileage compares with it.

Thanks for your detailed response. I really liked it.

 

Do you have any pics on of your Scangauge and how you have it mounted? This would be very useful in figuring out how the engine responds to 91 vs 87.

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I did several tanks of 93 octane for the first few months, but now use exclusively 87. I saw MAYBE a 0.5 mpg difference, but premium is 50 to 60 cents more a gallon here in Fort Worth. I calculated that I'd have to average 3 mpg better to make premium worth the $$$. It ain't worth it.

 

Additionally, another member here who tunes a bunch said that there is no sensor to determine octane, only knocks and ethanol. So technically there should be no gains from using premium other than preventing HP robbing knocks. Use of a top tier 87 octane should also be sufficient. If you're looking for max bang for the buck, stick with regular gas.

 

E85 can be a wash if you can find it cheap enough. There are no cheap E85 stations near me. Actually, there are only 3 or 4 E85 stations in my county, so it ain't convenient either.

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Thanks for your detailed response. I really liked it.

 

Do you have any pics on of your Scangauge and how you have it mounted? This would be very useful in figuring out how the engine responds to 91 vs 87.

 

I have it mounted on the dash near the driver side A pillar with the cord running down the groove between the door seal and plastic trim. I've been monitoring timing, KR, oil temperature, and usually throttle position (currently set to engine coolant temperature when I took pick). From what I've seen with the ScanGauge is engine coolant temp matches gauge pretty close (usually 206-209). Engine oil temps usually is about the same as engine coolant temp but takes longer to reach peak (20 minutes or so). Highest oil temp I've seen is 219 when towing my boat with 80 degree ambiet temps.

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I hate to say this, but whom ever said there is no ethanol sensor in the trucks is wrong. In order the trucks to run E85 it has to have the ethanol sensor. There is a low/high octane timing map for gas and ethanol in the ECM.

 

Whether the ECM is in the high or low map depends on if the ECM is seeing any knock. So many degrees of knock for some much duration will force the ECM to drop into the low octane timing map until the decay period lapses, then it will transition back into the high octane timing map.

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My average on Trip A over the last 450 kms is 13.4l/100km which is around 17.5 mpg. However my best in the last 50km is showing 9.34l/100km which is about 24 mpg after doing a smooth highway run. Also a few weeks back I took the family down to Pennsylvania and the average on that 700km trip was in the 9's l/100km as well. They definitely rock in the open road.

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just got back from a fishing trip, my truck is the crew cab 4x4 with the standard box, 5.3 and 3.73's

I drove just over 1300 miles mostly highway, some 55MPH some 60 and alot 65.

I had 4 big guys and a bed full of coolers and gear and had a strong headwind coming back.

MPG for the trip was 20.0--I was very happy with that.

My truck only has 2300 miles on it now so it may get a llittle better yet.

The v4 mode works great dont understand why anyone wouldnt want it.

My best 25 miles was 24.4 MPG which I think is great.

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