I get REALLY BAD Gas mileage. What's wrong?!?!

I have a 1979 Fiat Spider. I have tested the miles per gallon about 3 times and each time it is really bad! I've been getting like 11, 12, and 13 mpg. But I dont understand why?

I just did a basic tune up and am hoping that will improve it, but I dont think it will do that much. I just replaced the condenser, plugs, fuel filter, oil, oil filter. Just the basics.

But is there any reason why it would be getting such poor mileage? It should be getting at least about 18-20mpg right?

Any suggestions?

Thanks! Jacob

You should be getting 20+ mpg. Check and reset your ignition timing. Check your carb and make sure the choke is releasing after the engine is warmed-up.

I think I found the source of the problem...well at least part of the problem. I looked at the choke, it actually wasn't closing at all...so it just stays open. Which shouldn't be a problem on the mileage...right?

But when I looked at the air cleaner assembly, I noticed a problem. I don't know the name of the part but its the part that opens and closes to allow hot or cold air to the carburettor, right before the carb. It was broken, so it was pretty much stuck and only letting in hot air from the engine. I bypassed that part by just tie strapping it, so now it doesn't let in any air from the engine in the carb. I realize that it will take longer to warm up...but this should help with my problem right?

Thanks...Jacob