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1975 280z mpg


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I just recently took a 900 mile trip to southern California, bay area to san Diego. I wanted to share my car and engine specs in accordance to my mpgs from my trip.

 

In a distance of roughly 900 miles I maintained about 22mpg average at an average speed of 75 miles per hour.

 

Engine and car specs.

-Engine timing set to 8 degrees tdc

-4 speed transmission

-enkei 92 rims (16x7) with correct tire size for stock setup

-all smog equipment removed except for charcoal canister

-tire pressure at 35 psi,tire tread at 80%

-r180 differential with a 3.54 gear ratio, New fluid as well

-10/40 full synthetic with a quart of Lucas oil stabilizer, fresh oil change

-using a 280zx turbo fly wheel and clutch combination.

-minimal weight loss on car, no ac or spare tire.

-rebuilt l28 engine with an N42 head and stock cam (all cam lash within correct stock spec), stock exhaust manifold with a custom exhaust system which includes a resonator and magna flow muffler.

-champion 3 core aluminum radiator, maintained perfect temp entire trip.

-cleaned and polished throttle body

-completely new set of after market injectors with new enjector plugs.

-New spark plugs, plug wires, rotor and rotor cap.

-repacked wheel bearings

-kyb struts with coilover suspension, set 2 inches lower than stock height.

-brand new engine mounts, diff mount, transmission mount, and every single bushing replaced, even the spindle pin bushings.

 

Overall an excellent trip, there wasn't a massive mpg loss once I hit the grapevine suprisngly, I only lost about 1 mpg with such a huge incline from the mountain which I believe is about 12 miles full distance. Most of the trip is basically flat land on highway 5, I'm pretty sure I could of gotten 23 or 24 mph if people weren't so bad at driving and weren't constantly causing me to break my momentum. I also experienced issues with heat soak every time I stopped to refuel since I have a non egr intake manifold with no heat shield.

Edited by stav2201
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I had slightly better mpg in my 280zx when it was "stock". About 25mpg. That was from Los Angeles to Daytona Beach, FL. I had a slightly larger wheel diameter and a 5 speed that I'm sure helped. 

 

Stock meaning, it was stripped, had a shaved non egr intake (with charcoal canister) and headers with a 2.5" exhaust system. 

Edited by BluDestiny
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After a long haul on the Freeway, I always pop the hood on all of my Cars ( Audi, Camaro, Datsun 280Z ) when I refuel. Lets all the stinkin' hot air out of the engine bay. After I refuel, I check the oil level, PS level etc etc, Then I'm on my way. Haven't had any Vapor Lock issues with any car since I adopted this procedure.

 

Nice to give the engine a quick look over to make sure nothing is amiss.

Edited by Chickenman
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  • 3 weeks later...

After a long haul on the Freeway, I always pop the hood on all of my Cars ( Audi, Camaro, Datsun 280Z ) when I refuel. Lets all the stinkin' hot air out of the engine bay. After I refuel, I check the oil level, PS level etc etc, Then I'm on my way. Haven't had any Vapor Lock issues with any car since I adopted this procedure.

 

Nice to give the engine a quick look over to make sure nothing is amiss.

 

Yes, i adopt this method now, venting the air out of your engine bay reduces the duration of vapor lock quite dramatically.

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I've kept mpg records on my 1977 280Z for 24 years now.  The first 11 years was with the stock L28 with between 100 & 200,000 miles on it - that's how far I drove it in 11 years. After that it was with the LS1.

The L28 originally had the 4-spd with the 3.54: R200 and then later an '83 280ZX 5-spd and 3.90 R200.  With both set-ups i saw as high as 24 MPG on the highway but pretty much averaged 19-20 in combined city/hwy driving.

Interestingly the LS1 with a T-56 and a 3.70:1 R200 does about the same - unless I'm in full aggressive mode and then it drops to the 10-13 MPG area. :-)

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