How to adjust oil in recipe when adding peanut butter I made a peanut butter cake, but it had too much oil. I used a recipe I'm familiar with, but added peanut butter to it. I used natural peanut butter (only contains peanuts and a little salt). 

How much should I cut back on the butter (the only oil in my recipe) when adding peanut butter? Do I need to adjust the eggs as well? I used approximately 1/3 c peanut butter for a single layer cake.
Natural Peanut butter is about 50% fat, butter is about 80% fat. If you want to maintain the original amount of fat in the recipe, you would decrease the butter by 60% of the amount of peanut butter you used. So if you used 1/3 cup of Peanut butter, subtract about 1/5 cup (a little less than a 1/4 cup) of butter from your recipe. Don't adjust the eggs. 

Hope this helps! I had to use too much math to get to the answer.