What percent of the overall value can I get from a car with serious mechanical problems?

I have a 2003 Honda Accord, and I really need to look into getting rid of it. Unfortunately, I bought the car (used) a few years ago ignorant to the fact that it burns oil. This is a problem that I have tried to rectify, but there's simply no solution but to keep adding oil every few days.
I keep the car in tip-top condition, but I really do not think I will be able to get much for it in the private party market. Out of a total asking price, what percentage of the value should I ask for?

How much oil does it burn? Does it smoke?

It very well may be drivable as is for years. Just make sure it doesn't run out of oil.

There really isn't a % deduction, I guess you just consider it poor condition.

Adding oil every few days is a heckuva lot cheaper & easier than paying thousands more for a newer car.

I drove an old car with a pretty bad oil leak for about a year. It was a $900 car and the repair was about $400-500. But adding a little oil about once a week was a lot cheaper.

I sold it to a guy who drove it years longer.

The key is never running out of oil. Running a little low won't hurt it. Running out will kill it.

The engine can also be rebuilt if you would prefer but that's pretty expensive.

And there's no guarantee the next car you buy wouldn't have problems too.

There's no such percentage for deduction of value for cars with problems. Generally, the value of the vehicle is its value, assuming no problems, minus the cost of fixing the problems. However… Potential buyers wouldn't buy it for that price -- they would simply buy the same car somewhere else without problems. So. In order to sell such a car, you would have to sell at significantly below the problem value of the car to make it worthwhile for someone to buy. People don't like buying problems unless it's a huge bargain and they don't mind the aggravation of getting it fixed.