Tom63050 Posted March 20, 2007 Share Posted March 20, 2007 My 91 Loyale 4WD 5-speed wagon used to get about 27 mpg, no matter what. Now it's getting about 21! Mods: 1. 3" lift, with aluminum 13" rims and 80-series Kumhos (These are 20 lbs lighter than the 14" steel rims and BFG Wilderness tires I had on before; at that time I was getting 27 mpg) 2. 40,000 volt coil, enlarged gap on stock plugs 3. new generic Bosch O2 sensor in cat I thought that the above mods would if anything increase mileage, but no. I pulled the disty cap; its contacts and the rotor's appeared pretty worn/pitted. So I'll replace these and see what happens. If this doesn't do it, any suggestions? Maybe some engine sensor went south, for example. Mileage is about 170K, so maybe the cat is getting plugged. Link to comment Share on other sites More sharing options...
daeron Posted March 20, 2007 Share Posted March 20, 2007 dont forget that changing tire sizes changes the mileage as recorded on the odometer, which is only accurate for stock tire size. If your mileage change has happened since you changed tire size, there is a serious correlation there that needs to be ruled out before you go saying you only get 21 mpg... I cant think of anything else to tell you for advice, but I thought I would mention that.. I hope it helps. Link to comment Share on other sites More sharing options...
Loyale 2.7 Turbo Posted March 20, 2007 Share Posted March 20, 2007 dont forget that changing tire sizes changes the mileage as recorded on the odometer, which is only accurate for stock tire size. ... True! ... Absolutely. But Also I Think it may be due to Clogged / Dirty injectors too ... so I Suggest to Check how much Size Difference is Between the 13" and the 14" Rims, along with their Tyres... to Figure a Better idea of What´s Happenin´ ... And to Clean the Fuel System can Help too. Good Luck! Link to comment Share on other sites More sharing options...
heartless Posted March 20, 2007 Share Posted March 20, 2007 tire diameter WILL make a definite difference in percieved fuel mileage! to find out the differences go here: http://www.1010tires.com/TireSizeCalculator.asp?action=submit put in the STOCK tire size in the first panel, then the size you are running currently in the second panel...you just might be amazed at the differences between the two. Link to comment Share on other sites More sharing options...
ivantruckman Posted March 20, 2007 Share Posted March 20, 2007 my gl reads 43 mph @ 55 mph with 195 -70 -15 27 inch od Link to comment Share on other sites More sharing options...
Tom63050 Posted March 21, 2007 Author Share Posted March 21, 2007 dont forget that changing tire sizes changes the mileage as recorded on the odometer, which is only accurate for stock tire size. Right, I know about the speedo/odometer slowing down. My 185/80x13 tires are only about 8% taller than stock 175/70x13, and I'm allowing for that. Going from 27 to 21 mpg is about a 23% drop. My tires are 2.9 lbs heavier than the same tire in stock size, but that is more than offset by using aluminum rims. And anyway, with the former 14" steel rim/BFG Wilderness setup, which was 20 pounds heavier per wheel/tire, I got a true 27 mpg after correcting for odometer error. So, anyone know whether any sensor failures could result in poorer mileage? Link to comment Share on other sites More sharing options...
daeron Posted March 21, 2007 Share Posted March 21, 2007 Sorry I was lazy about doing the math, but to answer your question, yes, some sensor failures certainly could cause this sort of problem. Visit the USRM (link at the top right of the page) and go to the engine electrical section, and find the write up on pulling the codes off of the ECU. There is also a diagnostic mode of the ECU that you can use to isolate further potential issues. Are you having any other running issues? accelerating good, no backfire? Pull your plugs, what do they look like? Link to comment Share on other sites More sharing options...
kingbobdole Posted March 21, 2007 Share Posted March 21, 2007 air filter, O2 sensor, oil change... Also realize that higher profile vehicles with now wider tires increase your air drag greatly. My MPG dropped once I got my lift and tires on as well.. I was getting a cool 32 MPG or so stock and now I can barely make 25 MPG... I don't see it as too much of an issue... Link to comment Share on other sites More sharing options...
heartless Posted March 21, 2007 Share Posted March 21, 2007 larger tires = bigger contact patch = more "rolling resistance" coupled with higher profile....these things will affect fuel mileage. it isnt just a "weight" issue. i suspect you are looking for demons where there are none. heck, even an aggressive "off road" type tread pattern vs a smoother street tread pattern in a stock size would create differences in fuel mileage... if fuel mileage is a big concern for you, go back to the stock size tires. Link to comment Share on other sites More sharing options...
mikeshoup Posted March 21, 2007 Share Posted March 21, 2007 His tires are marginally larger than stock. I run 185/80/13 on my EA81T wagon and it sounds like I get better gas mileage. (And this thing sucks for that!) Change: O2 Sensor Spark Plugs, wires, cap, rotor Air Filter See where that leads you. All of those can drop gas mileage. Link to comment Share on other sites More sharing options...
psylosyfer Posted March 25, 2007 Share Posted March 25, 2007 Larger Diameter tires improved my hiway mileage, But degraded my acceleration enough to notice, and slightly lowered my stop and go mileage. Which makes sense as they travel further with each revolution, but use more power (or the same for longer) to get rolling, Everything is a compromise Link to comment Share on other sites More sharing options...
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