Winter Mileage
Rookie
Joined: Feb 2007
Posts: 53
Likes: 1
From: MD
I've only put a little over 1,000 miles on my 400h, but so far averaging about 26.5 mpg in temps ranging from teens (mornings) to mid 30s (afternoons). I have used premium, mid-grad and regular and I have noticed no difference in economy between the three.
I do suspect that winter temps and winter gasoline formulations will tend to reduce economy overall, so I'm hoping for better MPG in the spring.
I do suspect that winter temps and winter gasoline formulations will tend to reduce economy overall, so I'm hoping for better MPG in the spring.
Rookie
Joined: Nov 2004
Posts: 88
Likes: 2
From: California
The heating value (Btu/lb) of 92 and 87 Octane gasolines are basically identical, so there is no reason they should result in different mpg. Many tests have verified this. Ethanol has 2/3 of the HV of gasoline, so obviously it will lower mileage, depending on the percentage in the gasoline.
Last edited by riwyle; Jan 28, 2014 at 03:51 PM.
Pit Crew
Joined: Nov 2010
Posts: 129
Likes: 9
From: On
hmm, i am tempted to try 87 again.
The heating value (Btu/lb) of 92 and 87 Octane gasolines are basically identical, so there is no reason they should result in different mpg. Many tests have verified this. Ethanol has 2/3 of the HV of gasoline, so obviously it will lower mileage, depending on the percentage in the gasoline.
The heating value (Btu/lb) of 92 and 87 Octane gasolines are basically identical, so there is no reason they should result in different mpg. Many tests have verified this. Ethanol has 2/3 of the HV of gasoline, so obviously it will lower mileage, depending on the percentage in the gasoline.
There is at least one reason why mpg will suffer with lower octane. Lexus recommends 91, and if lower octane is used the ignition timing is retarded under load to reduce pre-ignition knock.
This is why power is also reduced with lower octane gas. As per the Lexus hybrid interactive guide:
3. Ratings achieved using the required premium unleaded gasoline with an octane rating of 91 or higher. If premium fuel is not used, performance will decrease.
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