I've been searching through some old threads for an answer, but could use some help. My 96 SL (210K) has been getting 33-35 MPG average, but dropped off to 25-28 MPG. I tried new NGKs, plug wires and just installed an engine coolant temp sensor. There is no "service engine" light on now, but a month or so ago it came on for one day and then went out.

The car runs smooth, idles good, and has no drop in power I can tell.

It has been wicked hot here in Phoenix this summer and the AC is on constantly, but I don't remeber from years past it affected the MPGs this much.

What should I look at?


Larry

 

Check your tire press, check air filter, blah blah blah, basic car care. If all of those are ok running a bottle of seafoam or fuel system cleaner though a tank of gas might help.

if not, I would be happy to get 28 MPG out of a 15 y/o car.
If the Service eng. light comes on take it to a pepboys and have the code read that might point you in the right direction.

 

sounds like ECTS -- did you replace ECTS and connector with GM sourced parts?

 

I got a "Duralast" from AutoZone, and re-used the connector as they didn't have it. The connector looked ok. Should go OEM? How can I be sure the GM dealer has OEM? In a delco box?


Tires are up, no drag on car, if I throw it into neutral it coasts forever and loses speed very slowly. I'm kinda a "hypermilege" driver, always reading the lights way ahead and coast a lot.

 

I would always use the OEM ETCS and the connector is only OEM. Thermostat is another culprit that can cause sudden in mpg drop.

Oh and it has been damn hot for a damn long time and the fuel mileage of all three of our cars has dropped more than a fair share. It's just that the drop off has lasted longer then normal with this heat.