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As I was replacing the thermostat I thought I'd take the opportunity to measure the MPG pre and post stat change. I did this as I heard some reports that MPG would be improved following replacement of a faulty stat. Before the stat was replaced the temp gauge never got above 70 degrees, it now sits at 90 when it gets up to temperature (after about 10 mins of driving).

Results are as follows:

Pre stat change: 38 MPG
Post stat change: 37 MPG

No real change in driving style or type of driving. Car is a 156 2.4 JTD.

Just posting this because I thought it may be of some interest...
 

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Didn't notice any MPG increase either after both changing on both my machines. Both 2.4 JTD's
To make matters worse, also noticed performance reduction too..... (even after ECU reset) WTF?
 

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Won't change mine then :) - was the MPG measured on Motorway or long runs, or just around town - as thats poor mileage from a JTD if on a run?
Did you change the stat yourself? I'd like to know if you had any problems or top tips
 

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I changed the stat on my 2.5 V6 a couple of months back and noticed a slight increase in my MPG figure. 38 mpg would be a dream of mine!
 

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Won't change mine then :) - was the MPG measured on Motorway or long runs, or just around town - as thats poor mileage from a JTD if on a run?
Did you change the stat yourself? I'd like to know if you had any problems or top tips
MPG measured for a full tank of driving. Driving involves daily commute and running around at the weekend. Daily commute involves about 10 miles of motorway, 4 miles dual carriageway and 6 miles of b roads. I must admit that I was hoping for over 40 MPG. I don't exactly drive it hard on these journeys. Tyre pressures are all correct and checked weekly. Anything else that could be causing poor MPG?

I didn't do the stat myself as I got it changed when they did the clutch. I would have though under normal circumstances. I believe that it's pretty straight forward (one tricky bolt?). Be sure to flush the system and fill will fresh anit-freeze while you are at it though, rather than just topping up.
 

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Well was getting 40-50MPG, depending on trips, before and roughly the same after. What dissapointed me most was the power loss.
One replacement was done by Alfaworkhop and the other by myself. Don't really think where you get it done makes any difference TBH.
 

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As I was replacing the thermostat I thought I'd take the opportunity to measure the MPG pre and post stat change. I did this as I heard some reports that MPG would be improved following replacement of a faulty stat. Before the stat was replaced the temp gauge never got above 70 degrees, it now sits at 90 when it gets up to temperature (after about 10 mins of driving).

Results are as follows:

Pre stat change: 38 MPG
Post stat change: 37 MPG

No real change in driving style or type of driving. Car is a 156 2.4 JTD.

Just posting this because I thought it may be of some interest...
1 MPG is well within normal variances in fuel consumption - even with similar driving styles and usage patterns. Road, traffic etc conditions will never be exactly the same so neither will fuel consumption. This is certainly no indication that changing the thermostat has made your fuel consumption worse.
 

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Changed mine a few weeks back, mpg was alot better after but mine was getting now where close to 70 deg unless had been sat in traffic for ages
 

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Main reason to change them is the engine warms up faster which means less wear and Warmer Footsies in Winter ;)
 
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Are you guys driving the 2.4 10v? Because mine (2.4 20v) doesn't get anywhere near those figures - best I achieved was something like 7 l / 100 km = 34 mpg. The conversions are made with Google (type "xx kpl to mpg" or the other way around), so I don't know whether it uses the big (imperial?) gallons or the small (American?) ones.

Edit: figured out, Google uses US gallons (strangely, even when trying to do the conversion on google.co.uk).

7 l / 100 km = 34 mpg (US gallons)
7 l / 100 km = 40 mpg (Imperial gallons)

Another "problem" has gone away, I suppose my car's fuel consumption is normal.
 
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