In my experience.... little to none at all. Last year I had no open TL's other than a student loan and tons of baddies.
1. Traditional lenders wouldnt finance anything -- even with 3K down... including a 6K used car which would have been a 50% DP.
2. I went to a subprime lender- CNAC ( JDByrider ).... all 3 scores jumped 10-15 points... and even with a year of on time payments I never saw another jump until I added a major card and saw about a 15-20 point jump on EQ & TU.
Other people I have seen with auto loans dont seem to be getting any scoring help.. or anything like what happens with credit cards. I think thats the main reason why Auto lenders use an Auto Enhanced Fico because a regular fico score tends to be more biased towards credit cards and not auto loans.
Now if you have a clean history... you might have better results.