760 GLE/1987/Gets average 16 mpg

ryanuenchow · Post by **ryanuenchow** » 11 Jun 2009, 11:25

I purchased my 1987 760 GLE almost a year ago and it got 20+ mpg but now since winter started and is gone now im getting 16 mpg on a good day..what might be the cause of this and how can i go about fixing it. She is a fuel injected, automatic 2.8 V6 if that helps any. Any advice would be helpful.

Post by **billofdurham** » 15 Jun 2009, 12:21

How long is it since you checked/replaced service items:
plugs; plug leads; air filter; fuel filter; throttle valve; mixture adjustment?

Other things to check when fuel consumption is excessive: connectors on air mass meter; air control valve; coolant temp sensor; knock sensor; injectors; all earth (ground) connectors on the inlet manifold; air leaks between air mass meter and the engine; all connections, joint couplings, seals and hoses on the intake manifold and throttle housing. If necessary clean the throttle housing.

Bill.

ryanuenchow · Post by **ryanuenchow** » 15 Jun 2009, 14:26

I've replaced the plugs with new original plugs about 3 months ago. Air filter about 6 months ago. But haven't done plug leads, fuel filter, throttle valve nor mixture adjustment. I don't really know much about cars or how to fix them... are these items pricey? Do you know of a good site to get these items at a good price?

Thank you for your response though I will try and get someone who knows where and how to replace these things. Also do you know a rough estimate of the MPG i should be getting? I've looked around on the net but i haven't found a steady number, everyone says differently. (its a 2.8 V6)

Post by **billofdurham** » 15 Jun 2009, 15:30

For prices check out the two sponsors at the top of the forum: IPD and FCP. Also check out http://www.eeuroparts.com/Main/Home.aspx.

The throttle valve/housing shouldn't need replacing just check to see if they are clean and adjusted correctly.

Also do you know a rough estimate of the MPG i should be getting?

You will get all sorts of figures thrown at you on this one as everybody drives differently. You have a heavy car with a large engine and a 4 speed gearbox so you can't expect a great mileage return especially if you accelerate and brake hard.

Bill.

ryanuenchow · Post by **ryanuenchow** » 24 Jun 2009, 12:26

Thank you yet again for the wonderful response, but surprisingly all I really needed was a gas cap.... it almost returned my mileage back to normal. Getting 200+ miles on a full tank! Next it my oil, which should also help a little bit.

FCPEURO · Post by **FCPEURO** » 24 Jun 2009, 13:54

Gas cap? What was happening, it was leaking, or just the fuel tank's atmospheric pressure was different then it should be or something?

Interesting how that can make such a big difference, wow.

Post by **billofdurham** » 24 Jun 2009, 15:41

Has it made such a difference? Maybe I am looking at this the wrong way but the 760 has a 15.8 gallon (60 litres) tank. When the gauge goes into the red section there is about 2.4 gallons (9 litres) left in the tank. If the refuelling is done at this point, thereby using a 'full tank' without taking the risk of running out, and being generous and taking 200+ miles as 230, this is an average of 17mpg or if we say 250 miles then it is still only 18mpg.

I love playing Devil's Advocate.

Bill.

Tiki · Post by **Tiki** » 24 Jun 2009, 22:38

FWIW I have an 89 760 GLE with the V6. I get about 18 to 20 mpg. It seems to me that it varies more with the quality of fuel than the way I drive. My fuel gauge is broken so I use the odometer to know when to fill up. So I keep pretty careful records.

Bill, I think my tank is just shy of 19 gals. At least I've put that much in at one time.

ryanuenchow · Post by **ryanuenchow** » 25 Jun 2009, 12:35

I guess the gas was just evaporating out of the tank because there was no cap (where you pump fuel into) and I was unaware that it was 15.4 gallons to a tank...i was thinking more along the lines of 13.5 but then again i never really go much past the middle of the red part of the gauge. Looks like Im just gonna have to fill her up and drive her till she runs out to get the true readings out of this. All I know is that with just putting a gas cap on i get 2(18mpg)-3(19mpg) miles better a gallon.

And I also have notice that the quality of the fuel also makes quite the difference, I've came across going to a more corporate gas station (BP or Shell) rather than the smaller independent gas stations always have better gas in which i get better mileage. I always reset my odometer every-time i refuel to insure my car is running consistently.

Post by **billofdurham** » 26 Jun 2009, 12:47

Bill, I think my tank is just shy of 19 gals. At least I've put that much in at one time

The specification sheet for the '89 model shows a tank capacity of 21 gallons. However, the on-line owner's manual shows 15.8 gallons. VADIS parts numbers are different for '87 and '89 so I would go along with the bigger tank on the '89. Or are you one of these magicians who can get a gallon into a tea cup?

Bill.