I have heard of using vegetable oil and also olive oil. Probably will even work, too. If you are just dying to try it, use VERY small amounts and be sure to remove the excess a minute or so later.
Either way, I suspect that you will find your seats will become dirty even quicker after trying it. Both oils tend to hold dust and dirt pretty well. Not to mention the failure and breakdown of such oils when subjected to high temperatures (such as being left in the summer sun with the windows closed.)
If you're not just dying to try it....I've a better idea which might even be cheaper.
Get yourself a tin of saddle soap and a tin of mink oil. Both can be found at most any well stocked grocery for probably something like $3 each. Usually, they are shelved with the shoe polishes.
Use the saddle soap to clean....and the mink oil to preserve....as per the label directions, of course.
Hate to say it....these two will out do just about any commercial leather cleaner/conditioner you're ever likely to see. And, they are dirt cheap. I have used them for years on auto leather, leather home furniture, leather coats, and even leather wristwatch bands.
.....sT