70 - 100 lower gas mileage after major service done Chrysler minivan

A couple of weeks ago, I had a major service done, 90k miles where at least the pcv ( ? ), spark plugs, air filter was replaced. When I filled up the tank, my roof console read Distance to Empty as only 248 miles…I thought this is wrong…it usually reads 352 miles. I zeroed out my odometer and I only got 270 miles for that tank of gas…NOT GOOD ! Any ideas ? What happened to my minivan’s gas mileage ? Why this HUGE degredation ?

2001 Chrysler town and country minivan, 6 cylinder, longer wheel base. I’m on my 2nd or 3rd tank of gas with the same dismal results.

Take it back to where you had the service done and have them check out their work…

It could be as simple as mixing up a couple of spark plug wires. Bring it back in and it should be an easy fix.

However I would suggest, that if you want to measure your mileage, do it the right way. Fill the tank and record the mileage. Next time fill the tank, subtract the miles you recorded at the last fill up from the current miles and divide by the number of gallons. Doing that several times in a row will give you a very accurate number. Miles per tank can vary a great deal.

They could have put in the wrong plugs or broke a plug wire. They could have left a connector off. Do as the other suggest and take it back, give them a chance to make it right. Just explain the problem to them as you have done here and I’m sure they will get it right.

No switched or broken spark plug wires or the “Check Engine” would be on from a severe misfire. (It’s not on is it, Mlotus?) Incorrect plugs would be a possibility, though. How is the engine running?

But heed Joseph’s advice about calculating your fuel economy, though. At least use the average fuel economy function instead of DTE. I have always found this to be fairly accurate in my Chrysler vehicles.

The computer has no magic sensor to determine how many miles are in a tank of gasoline. The distance to empty is determined by the average mileage stored by it. When your car was in for service, they probably disconnected the battery, resetting the handy little trip computer to default, and losing all stored data. Give it a few tankfuls to return to normal. And don’t rely on the gadget to accurately determine what mileage you’re getting. Fill up, reset odometer, and next fill-up, divide miles by gallons needed to fill the tank. This is the only accurate way to determine what mileage you’re really getting.

You need to either run it for a while longer across many more tanks or simply use the trip odometer divided by gallons used to figure out your MPG.

I took it back this morning to the Chrysler dealership. The minivan seems to run ok…no check engine lights or anything abnormal about the dashboard. No funny noises etc. It is just the gas mileage is way off…The dealership insisted that the diagnostics ran fine and they rechecked the new plugs. They couldn’t find anything wrong with it. They suggested that my gas station was using too much ethonol and that is why my mileage is down by about 80 miles. I had filled the tank for the 4th time this morning and still the DTE only showed the 252 miles. Again I have zeroed out the trip reading to check this tank’s mileage. The DTE overhead console and the trip odometer are 2 different gauges which indicate my minivan’s mileage. I went into the gas station ‘Al Prime’ this afternoon to ask them if they new if the gas mix had been changed. The posted ‘gas’ sign read at no more than 10 percent Ethonol…the gas attendants said the city comes in and checks the mixture every now and then…plus they have had NO changes in their gasoline content. I’m thinking of going to another gas station after this tank is done to see if the gas is an issue. However, I’ve had a friend fill up at the same station and asked they check their gas mileage too. I think the dealership service dept. somehow caused this issue. I may have to go to another dealership to see if they can ‘earn’ my business back. I had the oil changed again today to see if that somehow would make an impact. I told the oil filter guys about my gas mileage dilemma and they did a quick check for me and they said the air filter etc. was new. Ok, so I have reset the trip back to zero again with this 4th full tank…the previous tank only netted me the 270 miles…but I will check this tank…it will take me about a week or so to go through it…I’ve been trying to conserve gas. : ) Any other ideas out there ? thanks…

But when you fill up and divide the miles you’ve driven by the number of gallons it takes to fill the tank, what miles-per-gallon result do you get? Are you zeroing the trip counter and using that, or are you using the DTE on the trip computer?

Something is wrong. Too bad the dealer thinks no check engine light, no problem. Its a little late now, but do you remember looking at the tachometer at various speeds, like what rpm did the engine run at when doing 60 mph? Is it the same now? Can you discern 4 distinct shifts when accelerating plus the drop when the torque converter locks up? If they changed the transmission fluid at the service and put in the wrong transmission fluid as a replacement, it could be causing the transmission to either slip or not allowing the torque converter to lock up. The transmission can really affect fuel economy.

Did they do any brake work. If they did something to cause the brakes to drag, this would also cause poor fuel economy. On a empty road, go about 25 mph, put the car in neutral and see how far it coasts. You will probably need to do this with another vehicle as a comparison.

One last thing, did they change any oxygen (O2) sensors?

One more time: You can’t rely on the DTE function to determine fuel economy, especially with a full tank!