2.4L mpg, 4th vs. 5th gear (Difference of 4.5 mpg)

[ned23]

I "accidentally" did an experiment this week. I took my 09 2.4L Vibe with 5-speed auto on a road trip and the car was inadvertently driven 122 miles in 4th gear by my passenger. We figured it out when the second driver asked:"Why does it say "4" here on the dash?"Anyway, I realized this madea good comaprison, so I decided to pull over and fill up to get a mileage comparison. Here it is:First tank (5th gear, 95% Hwy): 311 miles / 11.09 gallons = 28.04 mpg.Second tank (4th gear, 100% Hwy): 122.7 mi / 5.2 gal. = 23.59 mpgBoth on same highways one on return trip. Cold winter driving, 5-15 degrees F, with intermittently snowy streets.

[RIT]

Makes sense - ouught to be related to the gear ratio between 5th gear and 4th gear. Don't know the actual gear ratios, but generally, rpms drop by about 20% for each gear change.

[file014]

wouldnt 4th be 1:1 in a 5 speed, with 5th being overdrive? on the engine with that much torque, they should have 6 speeds, 2 overdrives. It does 31 mpg in a camry and only 28 in a vibe? something aint right.

[prathman]

I was expecting to see something similar with our '87 Chevy Nova (Corolla clone - also a NUMMI product) when it lost 5th gear about 60 kmiles ago.But surprisingly I noticed no decrease in mileage at all. Still got just over 45 mpg on long highway trips, same as earlier when 5th gear still worked. But the engine noise is certainly more now that I have to use 4th.

[jake75]

Quote, originally posted by ned23 »I "accidentally" did an experiment this week. I took my 09 2.4L Vibe with 5-speed auto on a road trip and the car was inadvertently driven 122 miles in 4th gear by my passenger. We figured it out when the second driver asked:"Why does it say "4" here on the dash?"Anyway, I realized this madea good comaprison, so I decided to pull over and fill up to get a mileage comparison. Here it is:First tank (5th gear, 95% Hwy): 311 miles / 11.09 gallons = 28.04 mpg.Second tank (4th gear, 100% Hwy): 122.7 mi / 5.2 gal. = 23.59 mpgBoth on same highways one on return trip. Cold winter driving, 5-15 degrees F, with intermittently snowy streets. In my experience is is hard to draw conclusions from just one fill-up, especially a 5 or 10 gal fill-up. The pump cutoffs can vary.