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View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)
Welcome to the forum, when you get a chance you should start a garage entry so we know what you own rather than asking all the time. Just kidding I don't care, but it comes in handy sometimes.
I'm pretty sure Costco gas is top tier gas as well as shell. Someone will correct me if I'm wrong.
Do you idle your car a lot? Ever check the air filter? The worst I've gotten was 27.8mpg hand calculated and that was with a few hours of idling, and mostly relatively short 14 mile trips in -13F to -31F weather.
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View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)
I've been getting ~52mpg indicated driving ~18 mi to and from work at 40-55mph, with the A/C off and windows cracked. Fueled up on Shell premium at 2 marks on the fuel gage. Fueled again with Shell regular and gas mileage dropped to 43mpg, but it was also raining, road was very wet.
Also had some Lucas fuel treatment (the thick stuff in a gallon jug) in both tanks, about 2oz.
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View my fuel log 2017 Mirage ES 1.2 automatic: 42.3 mpg (US) ... 18.0 km/L ... 5.6 L/100 km ... 50.8 mpg (Imp)