Yes! you read that right, the datsun gets 18mpg :] Since it’s first fill up, i’ve driven 226 miles on 12.5 gallons. And… that puts it about par w/ other 280z’s i think.
So NOT the fuel sipper that the Scion xB is, but better than expected!
Oil Pressure – I’ve noticed the fuel pressure gauge is reading somewhere below normal. Supposed normal pressure should be at 45 psi, but the gauge is showing ~30 psi. I’ve also noticed on longer drives that the gauge will noticeably drop over time. But it can’t be too accurate as the engine should auto-shut off at ~2 psi, and let me tell you, i’ve seen that gauge hit rock bottom before.
Now there are a few notorious things that could be the cause of this: 1) electric gauge is only an estimate, not as exact as a mechanical gauge, 2) oil pressure sending unit (or oil pressure gauge) is known to break down after a while, 3) possible oil pump, 4) need a thicker oil.
First thing i’ll do is check the pressure w/ a mechanical gauge straight from the engine. That’ll give me a true reading from which i can assess whether the dash gauge is correct or not. If so, I look at replacing that oil pressure sending unit. The “sending unit” is located next to the oil filter right on the engine block – kind of looks like a spinning top.
**Note** 1977 was a funny year – there are early and late models that have differences (ie. trunk deck shape). The Oil Pressure Sending Unit is also different: Early model had a bullet point terminal (shown here); Late models have the spade terminals. Also, it seems like general consensus that the Nissan factory units are better than the 3rd party brands.
Motorsport Auto has the proper one for my late model Datsun 280z: http://www.thezstore.com/page/TZS/PROD/17-8003
11/27/11 – Okay, so now i’m not so sure… my 280z was built in 4/77 which should make it an early model Z and it has the bullet type terminal (sorry NOT the spade terminals), but MSA has the spade terminal oil pressure sender for models made in 3/77-84! what gives?! So possibly the one i have is incorrect for the year. <- needs more research…