1

You need to ask on the Greece forum about there but here(please sit down to read this!),petrol is slightly over 4TL per litre and diesel slightly over 3TL per litre.So that is around 1.60€ per litre for diesel.....gulp.

2

I can help you with fuel prices in Iran

3

Unfortunately many of the newer cars need the unleaded 95 gasoline

(Approximate monetary conversions, check with a currency converter first)
1 gal = 4.55 liters
1 dollar = 1.52 TL
http://Unleaded (kurşunsuz) 95 is the most expensive.
If one (1) liter gasoline is 4 Tl or 2.6 USD
4.55 x 2.6 = 11.83 USD per gallon
An economical car will get about 15 km per liter.
You do the math...

4

In which country do they pay for imperial gallons with US dollars, I wonder. 1 US gallon = 3.79 litres.

5

DavidM1 has shown me the error of my ways (and my calculations) in which I mixed US and UK figures.
The US and the UK are "two countries united by a common ocean and separated by a common language."
Thank you for showing me the egg plastered upon my foolishly grinning face... I stand corrected O math(US) / maths (UK) wizard, and do apologize :-) I also decided I should add the Euro to the mix.
Please let me know if there are errors as math/maths was/were? not my favorite/favourite subject.

Currency Converter:
http://finance.yahoo.com/currency-converter/
Capacity and Volume Converter:
http://www.unit-conversion.info/volume.html

1 gallon UK = 4.55 litre (UK spelling)
1 gallon US, liquid = 3.79 liter (US spelling)
1 dollar = 1.5287 TL (as of Apr 20, 2011)
1 GBP = 2.4989 TL (as of Apr 20, 2011)
1 Euro = 2.2001 TL (as of Apr 20, 2011)
Unleaded (kurşunsuz) 95 is the most expensive.
If one (1) liter gasoline (benzine in Turkish) is 4 TL or 2.62 USD
3.79 (US) x 2.6 = 9.85 USD per gallon

If one (1) litre gasoline (benzine in Turkish) is 4 TL or 1.60 GBP
4.55 (UK) x 1.6 = 7.28 GBP per gallon

I do not know how the rest of Europe calculates their gallons...
If one (1) liter gasoline (benzine in Turkish) is 4 TL or 1.82 Euro
3.79 (US) x 1.82 = 6.90 Euro per gallon
If one (1) litre gasoline (benzine in Turkish) is 4 TL or 1.82 Euro
4.55 (UK) x 1.82 = 8.28 Euro per gallon

An economical car will get about 15 km per liter.
Now you can do the math...

6

As for Greece, you can have a look at:

http://www.4real.gr/FuelPrices/public/show-fuel-prices

Same application in Android Market:

https://market.android.com/details?id=gr.x4real.fuelprices.android