Originally Posted by RSK Property Maintenance
I'm sorry to break this to you, but you are the only one who know's if the gas or diesel you used is work related, there is no way to disprove that it wasn't work related, If you don't want to write off then you don't have to, but there is no way to disprove that it wasn't for work. Its pretty tough for anyone who isn't a first hand account to say you used the gas or diesel for personal use.
I'm afraid you don't know how an audit works. An IRS auditor doesn't have to disprove anything. At the start of the audit it is presumed that every deduction that you took is falsified and you have to prove each and every one if the auditor desires. If you can't prove something then they use industry standards as their benchmark. That usually doesn't work out real well for the person being audited.