Edwrai
Member
Having owned both, I’d say the 90 will give better mpg constantly. I regularly got 550-600 miles up a tank.
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What to look for when buying?
- Thread starter treeroy
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Having owned both, I’d say the 90 will give better mpg constantly. I regularly got 550-600 miles up a tank.
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Edwrai
Member
Tbh I don't think that's the best information to a perspective buyer as although I'm not doubting your personal experiences, I believe 95% of people who have owned both would say that there is a considerable difference in mpg between the majority of tdi 90's and 75's but in favour of the 75.
There will always be anomalies to this due to maintenance, tyres, modifications etc but in my experience the tdi 75 is overall far more economical and more reliable too due to it's simpler design, particularly a late amf ?
hydo14
A2OC Donor
On the topic of fuel the other thing of note is that the earlier TDI's (before some time in mid 2002) have a 34 litre fuel tank (with an option for a larger tank) compared to the later cars 42 litre tank. With a car so economical that extra 8 litres of capacity can add a lot to range. Although my earlier TDI 75 AMF with the 34 litre tank still gets me around 450 miles from full to fuel light on which is plenty (and certainly further than I can go without needing a stop).
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Proghound
Admin Team
Indeed, and it's worth noting that those nominal tank sizes are both conservative estimates. When filling a TDI, when the pump clicks off you can use the vent nozzle in the filler neck to expel trapped air from the tank and then put more fuel in. If driven say 50 miles after the low fuel warning, which is supposed to be at 7 litres remaining, this often allows you to fit in the entire nominal tank capacity, so in total you can actually have 3-4 litres more than that in the tank.
(NOTE: do NOT do this with a petrol engine, the extra space is needed for petrol vapour.)
(NOTE: do NOT do this with a petrol engine, the extra space is needed for petrol vapour.)
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Howey
Member
May i ask how many litres you get in yours from fuel light to full, i get around 25 without venting with my best 337 miles mine is the AMF with presumably smaller tank which i think is spot on for its usage. Is yours a standard map and gearbox?
Cheers
Howey
Proghound
Admin Team
Venting my 34l tank from the warning plus 10-15 miles, normally gives me room for 32-33l right up to the top of the neck. The pump I normally use slopes down to the passenger side so I know for sure there's no air trapped in there. That's normally about the 430 mile mark so about 60mpg. However I get more like 55mpg in the cold when the Webasto is working all the time - about 400 miles. That's all on my daily 20-mile each way mixed commute with a little urban shorter running thrown in.
Howey
Member
Good to know and mpg inline with mine but i thought the reserve fuel with have been 8 litres (not sure why i think that) but in that case wouldnt that mean your tank would be the larger 42l as to have only 1 or 2 litres left in the system having only done minimal miles with the fuel light on you would be getting some serious heat in that fuel
Proghound
Admin Team
I understand the reserve to be 7l, and I use maybe a litre of that before filling so 6l still onboard. I've always thought the true capacity of the nominally 34l tank with venting is around the 38-39l mark. From memory of my former Cobalt TDI its 42l tank would hold over 45l, I'm sure I actually put that much in it once.
Howey
Member
In which case i need to try the venting and report back!
hydo14
A2OC Donor
Yes I agree with 25 litres for a full tank if you fill up when the light comes on. I am probably setting slightly unrealistic expectations for the car in terms of distance and fuel economy. My commute is returning me between 74 and 78mpg hence I’m getting around 410 to 450 miles on 26 litres. I do not use the car for short journeys at all either as I live walking distance to shops
As far as I know my car is on the standard map and still (at the moment) has its original 5 speed gearbox. I do not get this sort of economy for motorway driving, the higher speed and revs seem to hurt the economy quite a bit.
Howey
Member
What speed are you doing to acheive such high mpg?
hydo14
A2OC Donor
To avoid further thread hijacking of this thread, and repeating of information I’ll direct you to my project thread on the car and what I am doing https://www.a2oc.net/community/index.php?threads/project-commuter.46201/page-3#post-467355
Edwrai
Member
Tbh I don't think that's the best information to a perspective buyer as although I'm not doubting your personal experiences, I believe 95% of people who have owned both would say that there is a considerable difference in mpg between the majority of tdi 90's and 75's but in favour of the 75.
There will always be anomalies to this due to maintenance, tyres, modifications etc but in my experience the tdi 75 is overall far more economical and more reliable too due to it's simpler design, particularly a late amf
I find that strange seeing the lower range torque and the higher gearing of the 90, the 75 always needed more revs. And the VNT is a more efficient turbo design a VNT is also used in the 1.2tdi
I would say it’s possible to get lower figures than a 75 in a 90 when driving harder.
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Edwrai
Member
Also worth noting if you look at Fuelly data the 90 averages higher than the 75 in the 2004 year, of course the 90 didn’t exist before then.
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Edwrai
Member
thanks for the advice and information, everyone who replied in here. It was very usefulI've now got an A2.
Great news, when you can you should upload photos!
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