HI guys I have a mileage question for you. I have a 1980 scout with 304v8, 89 gmc truck TBI, custom chip, vss, self heated O2 sensor, tuned by myself, with lean cruise initiated thanks to Mark works great. I have developed a pattern in mileage that is both frustrating and rewarding I've had this system for about 4 years now and the last 2 years i have had the custom chip installed, since then my mileage has increased greatly. For the last 2 years every time I go on a trip which is only a few times a year I get great mileage leaving home or after the scout has sat over night and is cold I will get 18-19 mpg's 5 times now using GPS to track mileage. This is going 60mph at 2400rpm on the interstate from gas station to gas station no driving around idleing. NOw on the way back I will fill up my vehicle to check mileage/ the scout will have only sat for say a couple hours while shopping and I will do the same on the way back go fill up and go directly to the next gas station to check mileage same route on the way back. I have done it 4-5 times now and one the way back it always drops to around 12MPG!!! I only have theories on this no real proof why this is and I would like to get to the bottom of it as it's driving my nuts....... Finally my most recent trip was a 3 hour route to hot rod power tour which is totally different route than i usually take to check mileage and the same thing happened 19mpg on the way down and 12 MPg on the way back!!! So now that I have nailed the same numbers on a different route using different gas stations to fill up I feel my numbers are correct.........
-Can someone please give me some ideas on what to look at that may cause this issue?
-Currently I have only used winaldi for data logging and it has been about a year since I hooked it up so my skills are rusty.... Is there a specific area to look at in a data log that would show a difference if I logged a trip down and back to see the difference?
-Is it common for a bad O2 sensor to cause an issue like this?? If so how can I test it?
-This has been driving me nuts for years now and I feel I must ask for help so any thoughts are appreciated!!!!!!!!!!
Thanks Brandon
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