new best city mpg Reply #15 – April 09, 2014, 09:54:10 PM Filled up with Premium 93 today, and got 26.3 MPG on the highway........24 on 87 usually. Quote Selected
new best city mpg Reply #16 – April 09, 2014, 11:49:01 PM Therr is less octane, therefore less power.People always laugh at me when i tell them i get best out of 711 gas, and worst out of chevron and texaco. Quote Selected
new best city mpg Reply #17 – April 09, 2014, 11:58:52 PM Quote from: MY83T;432045Filled up with Premium 93 today, and got 26.3 MPG on the highway........24 on 87 usually.I'm surprised you got a benefit. With the stock setup and stock timing you should see no benefit from anything above 87 octane. I run 93 octane in my Thunderbird but I've got the timing set at 18* BTDC. I run it for knock prevention. Quote Selected
new best city mpg Reply #18 – April 10, 2014, 12:05:29 AM Quote from: thunderjet302;432057I'm surprised you got a benefit. With the stock setup and stock timing you should see no benefit from anything above 87 octane. I run 93 octane in my Thunderbird but I've got the timing set at 18* BTDC. I run it for knock prevention.Not only have i noticed better mileage, but its running smoother also on acceleration with 93. I only put better brand fuels in my car also. Quote Selected
new best city mpg Reply #19 – April 10, 2014, 01:02:29 AM When we did the stupid ethonal switch, i got the equivilent if 108 octane due to the corn . i also lost at least 7% mileage per tank. i think i got some of my power back by bumping the timing up to the 16° range, but the car ran the same with better mileage when i filled up at the gas stations that had not converted over yet.i expirimented with higher octane. i saw no improvment at all. flying j gave me the best overall average. i honestly think it has more to do with you knowing you filled up with expensive gas. kinda like your sure the car runs better after you do plugs and wires, even though you forgot one plug.the only reliable way i found to improve gas mileage was to stay a constant 55mph. this would take me from 25-28 range to 30-35mpg range. every other trick i tried had no effect or made things worse. my best actual mileages have actually all been or rural highways through moutain passes with several hundred lbs worth of gear. When i drove to montana a day or two after i completed my t-5 swap, i brought all of my had tools, two spare tires, my 4 ton floor jack, two jack stands, and several more hundred pounds or work tools, parts and equipment, plus mine and another guys luggage. I got pulled over three times and searched for drugs because my bumper was practically dragging. i averaged 28mpg (no odometer, based off of google maps), but also didn't include about 100 miles worth of driving the day before. if u added about 100 miles into the 15.8 gallons i put back in, it would have been well over 30mpg.When i tracked it everyday, same normal 52 mile route, i could go anywhere from 23mpg-30mpg without changing anything at all. not using cruise control was also good for about 10% increase. i also don't drive for best mpg. i always floor it wot on every on ramp and to get up to merging speed.the biggest problem with mpg, two identicle cars driven by two diffrent people can give very puzzling results. Quote Selected
new best city mpg Reply #20 – April 10, 2014, 01:19:35 AM Quote from: Haystack;432063When we did the stupid ethonal switch, i got the equivilent if 108 octane due to the corn . i also lost at least 7% mileage per tank. i think i got some of my power back by bumping the timing up to the 16° range, but the car ran the same with better mileage when i filled up at the gas stations that had not converted over yet.i expirimented with higher octane. i saw no improvment at all. flying j gave me the best overall average. i honestly think it has more to do with you knowing you filled up with expensive gas. kinda like your sure the car runs better after you do plugs and wires, even though you forgot one plug.the only reliable way i found to improve gas mileage was to stay a constant 55mph. this would take me from 25-28 range to 30-35mpg range. every other trick i tried had no effect or made things worse. my best actual mileages have actually all been or rural highways through moutain passes with several hundred lbs worth of gear. When i drove to montana a day or two after i completed my t-5 swap, i brought all of my had tools, two spare tires, my 4 ton floor jack, two jack stands, and several more hundred pounds or work tools, parts and equipment, plus mine and another guys luggage. I got pulled over three times and searched for drugs because my bumper was practically dragging. i averaged 28mpg (no odometer, based off of google maps), but also didn't include about 100 miles worth of driving the day before. if u added about 100 miles into the 15.8 gallons i put back in, it would have been well over 30mpg.When i tracked it everyday, same normal 52 mile route, i could go anywhere from 23mpg-30mpg without changing anything at all. not using cruise control was also good for about 10% increase. i also don't drive for best mpg. i always floor it wot on every on ramp and to get up to merging speed.the biggest problem with mpg, two identicle cars driven by two diffrent people can give very puzzling results.i don't dispute your results at all, but i can say that i tried my test one day apart. Same weather, road conditions, and cruise set at 60MPH. I then hit the reset on the MPG counter at the same marker as well. The mileage benefit was definite. As for the performance question, i had some noise on hard acceleration almost like a slight knocking, which has vanished with the 93 tankful. I ran the car down to 3 gallons remaining before filling with 93. I always fill up at the same local BP station too. I am driving Fox Birds/ Cougars nearly 30 years, so i am a quite familiar with the quirks. Def feel a difference. I may not be able to voice it in a super technical way, but the acceleration was smoother and less noisy. Quote Selected
new best city mpg Reply #21 – April 10, 2014, 05:39:34 PM Hmm there are two possibilities. One is that your Cougar has the timing advanced from factory specs. Not likely but it could have happened at some point. The other is that the car has carbon build up in the combustion chamber. It will ping on 87 but not on 93 if that is the case. As a fyi my 91 Mark VII with a 5.0 HO runs fine on 87 octane and the factory timing spec (10* BTDC). Quote Selected
new best city mpg Reply #22 – April 10, 2014, 07:56:33 PM I was thinking the same thing as thunderjet. There is no reason a stock SO 5.0 should need 93 octane if everything is working properly. The only other thing I can think of other than timing and carbon build up is maybe EGR valve stuck closed. Quote Selected
new best city mpg Reply #23 – April 10, 2014, 09:05:27 PM Heh, even cars I had that required/recommended premium, I put regular or mid-grade in and had no issues at all. Quote Selected
new best city mpg Reply #24 – April 10, 2014, 10:31:29 PM I'm not taking anything away from anyone, just sharing my experiances. gas mileage is a touch subject. different prople drive different ways and every little bit can make a big differance.As far as driving cougar/birds, i can gaurentee I've got near or over a half million miles on these cars. i put nearly 180k on my first 86 cougar, about 20k on my 87 cat, 40k on my second 86, about 50k on my second 87 cougar, 80k on my first and second 87 birds, about 60k on my current 87 bird and so far only about 5k on my latest 86 cougar. there's also a few other cars i never recorded mileage on or forgotten about. Quote Selected
new best city mpg Reply #25 – April 13, 2014, 11:14:48 PM Here is actual mileage on the Highway the other day, this was average after about an hour or so of driving with cruise on at 55-60. Quote Selected
new best city mpg Reply #26 – April 14, 2014, 12:36:38 AM So you don't buy into the 21mpg updated epa rating either?I'm not gonna have enough money to fill my car till friday to actually record mileage.my old 87 bird was fully loaded with the electonic cluster. calculating actual mileage over an entire tanks was generally 2-3mpg lower then what was actually calculated by the computer. less city, sometimes off. more freeway. Quote Selected
new best city mpg Reply #27 – April 14, 2014, 12:41:04 AM Oh, since i can't calculate this tank i too my mileage 380, added 10%(speedo is off by 15%. i just swapped more appropreately sized 235/60's out back) and that would be 19mpg over the whole 22 gallon tank. I'm surr i havent used it all obviously. i probably have more like 8 gallons left id guess, but nothing stellar.I'm gonna do a ton of driving next weekend. I've been without a full time pay check for a while. it will be nice to start getting one again Quote Selected
new best city mpg Reply #28 – April 14, 2014, 12:44:28 AM Quote from: MY83T;432296Here is actual mileage on the Highway the other day, this was average after about an hour or so of driving with cruise on at 55-60. My 90 LS, which of course, had the 3.8L, only managed to get around 20, but that thing was beat to hell. Quote Selected
new best city mpg Reply #29 – April 14, 2014, 08:32:05 AM Just a technical note- those onboard MPG displays have no real fuel consumption data being fed to them. They work from the VSS and Tach signals, IIRC. They probably have a base reference to go by, for instance, 60mph @ 2500rpm = 25mpg (or whatever). Any more MPH with less RPM equals X more MPG. Any higher RPM with lower MPH (such as climbing a hill) equals lower MPG. I don't believe it even uses the signal from the fuel sender (my sender in my old 87 went bad, and I believe the mileage computer still worked).You guys probably already knew that, I just figured I'd mention it just in case anybody new was reading this.EDIT- I was proven wrong- there is fuel data from the ECM provided to the cluster. Whoops! Quote Selected
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