1980 928 what size is my engine

[RCW]

I have an 80 928. I always thought that the engine was a 4.5, but after doing some reading I'm not sure.
One thing I read, you can find out your engine size by the last digit in your vin. Mine is 7.
I was talking with a tech who was texting with a guy at Porsche in Germany and he said it was a 5.0. Really?
I read, all 1980 American 928s have a 4.7 and they are really considered a 928S.

Who can give me a hand here?

[RCW]

My next question is about the oil pump. I had a guy come out to look at my car a few weeks ago. He said, he was concerned that the oil pressure was really low and it may need to be replaced.
When I start the car the oil pressure gauge always goes up and sits at 5. After I drive for a few minutes and the car idles down, it drops down to 1.5 or 2, and sometimes the red ! light flashes a bit, when I am stopped, like at a traffic light, but when I step on it it goes up to 3.5 or 4. I have owned the car since about 98, and it has always done this. IS THIS NORMAL?
A friend of mine has a '78 928 Euro and he said his oil pressure gauge always stays at 5. He also runs with 50 weight oil. I know his is a Euro, but he doesn't race it. I would think that 50 weight wouldn't be a great oil to use all the time, especially when it is cold.
would my oil pressure go up. OR do I need a new oil pump?

[Mrmerlin]

first what is the weight of the oil your using? How old is the oil?

It should be 15W 50 .
NOTE for chicago you could use 10W 40 in the winter but you may park the car during the winter,
Otherwise use 15 W 50 dino oil will work well.

if in any doubt change the oil and filter before changing the pump.
to find the engine code look at the the top of the block just under the top radiator hose about 8 inches forward from the water bridge clamp and then down under the hose.

You will find a flat surface with M28/ ?? the ?? numbers will tell what size engine you have just put the M28/?? into google

[riber.bentsen]

A 1980 US 928 can be EITHER a 4.5 OR a 4.7 (depending on whether it is an S or not - does it have spoilers front/rear?), but not a 5.0, unless it has been swapped. 5.0's didn't arrive until 1985.

You probably have the wrong oil weight in the engine, as stated above. If your buddys pressure is always pegged, the sender unit is most likely broken. It is very common, and most are. Easy fix, though.

[XLR8928]

If it's a US version, it has a 4.5L 220hp L-Jet motor. If it is a non-S euro, it should have a 4.5L 229hp motor. If it is a euro S, It will have a 4.7L 296 (300) hp CIS injected motor. (I'm sure I will be corrected if wrong)
-Kerry

[Alan in AZ]

Any car that always registers 5+ bar is not telling you the truth - regardless of the oil being used.

Likely the oil pressure sensor is wrongly connected.

You do probably have too low viscosity (weight) oil as noted above.

Alan

[Danglerb]

Last four digits of the vin is the serial number and goes up by one as each is assigned to a chassis, tells nothing about the car other than sequence.