houshold budget discrepency

My husband and I have individual bank accounts and want to create a joint account to pay our shared expenses (mortgage, insurance, utilities, groceries, etc.) but pay our auto loan payments and gas expenses individually. Due to the nature of my job, I have a higher car payment and spend much more on gas than he does. We want to calculate a percentage of each of our biweekly income to determine the contribution to the joint account by each person. The question is what to base the percentage on. The discrepancy is the due to the way I am paid by my employer. I am paid a base salary plus a fluctuating commission and I am reimbursed for mileage and office expenses on every paycheck. He thinks my reimbursements should be included in the total amount calculated as take home pay and contributed to the joint account percentage. This would leave me with little to nothing to pay the auto loan and gas expenses out of pocket because my reimbursement would be going into the joint bill paying account. He says this is the fair way to do this considering his company does not reimburse him for mileage so his checks do not include this extra income. He also drives 10 miles to work and back every day compared to my 500+ miles per week so he has a much smaller auto debt than I.
I want to do what is fair but we disagree on what that is. Please be brutally honest with me. What is your opinion on the fair way to calculate this?

Surely if you are married everything should go in together and all expenses/loans be paid together? What happens when you are on unpaid maternity or he loses his job?

Well I would be inclined to side with your seeing you spend far more on milage and office expenses.

However, as husband and wife you should be sharing everything including financial matters equally, after all isnt that what marriages are suppose to be about

I gather (maybe wrongly) you are in the States, this is an Irish financial website so culturally it may not suit your needs.

Why not come at this problem from a different angle? Work out your total average bi weekly take home including all mileage reimbursements,commission etc.Next work out all your bills including gas auto loans for an average bi weekly period.Take one from the other to leave your couples disposable income.Divide that by 2 to give an amount per person.Then,pay into a joint account the extra per person to cover all bills including auto expenses.Just my 2cents!