Ok so here is the deal. I have been thinking that I want to go crazy and get a super fuel efficient hypermiling car.
Both of these cars can get really good miles. Yes, the Insight is a Hybrid so it will get better mileage but with that you get more complexity, more expensive repairs and a much higher purchase price.
The 1988-1991 CRX HF should get about 50mpg fairly easily... and there is the potential to do a budget Civic VX engine swap and get into the 60mpg+ range. The purchase price would be about $3000.
The Honda Insight would be around 2000-2002 and should get about 63mpg. With additional driving efforts and patience people have been able to get lifetime MPG ratings into the 70-80mpg range. The Insight will probably cost $8500-9500.
The other wrench in my decision. I recently bought a 1998 Suzuki Swift. Its the 1.3liter manual and is in pretty good shape. As far as a commuter goes its a pretty good car. My thing is that if I am going to have a commuter I would rather have it be a car I like visually more then I like the Swift. This car has been getting 40mpg with winter tires on winter fuel... I just ordered up a set of LRR 13's that will go on the car and I hope will get me up to 45mpg.
Also FYI...
The Insight at 62.5mpg will save me $650/yr over the Swift at 40mpg.
The CRX HF at 50mpg will save me at least $220/yr over the Swift at 40mpg.
There are 3 CRX HF's that I have my eye on between $2200-$3200...
I have seen one, very very clean but $3200.
One needs body work at $2200.
One unfortunately has a d16 engine swap, but that will just speed along the VX engine swap ... for $2900
All prices before trying to 'deal'.