You need to get an analysis done to determine the damage and the repairs required and the Est Costs. Do not let the dealer who messed up your oil change do this - go to a different AUTHORIZED REPAIR DEALER. get a WRITTEN estimate. If there was any damage, the first dealer should to pay for repairs and provide a rental/loaner.
"Should, as with "if," spoils many a good story. So, you want to be prepared. Thus gather the FACTS and DOCUMENTATION to ESTABLISH
1. There was damage far beyond the loss of the oil at highway speeds.
2. Collaborating evidence articles affidavits (esp DEALER BULLETINS!) alleging the correlation between / causation of the damages found and the loss of oil at highway speeds.
With a third-party witness in tow, return to the negligent dealer and request the new piston rings/engine overhaul/replacement (indicated repair(s) required) per independent dealer/expert witness as well as reimbursement for any expense incurred in getting the estimate of damages/repairs required from the other Toyota dealer.
If the negligent dealer refuses, ask to speak to the manager/owner and document any statements made. You might also ask to speak to a factory representative and document anything he/she says by way of denying your requested repairs. (all witnessed o course)
Now, you know what's wrong. You know the negligent dealer refuses to repair your vehicle and his/their rationale and may even have the factory rep on record as well.
Assuming the negligent dealer's refusal made no sense at all and you firmly believe these repairs are needed and can be attributed to the loss of oil, you may consider a Small Claims Court action.
Someone wrote about a $10,000 limitation - but (as with a woman's right to chose) this varies from state to state so you need to check it out - easy online in most states. Then, I would suggest that you contact a Court Reporting Service that works in your local small claims venue - find out what they charge to transcribe a hearing in SCC. Trust me, having an official record of the proceedings made impresses the court (in this case, the judge. Mine asked "Why" I hired one and I answered "Your honor, if I lose the case, I would need the transcript for the appeal.") It didn't hurt my case (Against General Motors) at all.
You will also want to learn of all the fees involved. You will want to $erve the owner of the Dealership - so you will need to look that up (should be able to do so online) in state corporate records or local jurisdiction licensing office. It is likely you will not need to serve or even have anyone from the dealership that diagnosed the damages and estimated the repairs so long as you have that written (detailed) estimate in hand and can testify that you provided a copy to the negligent dealership when they refused to repair your vehicle.
If you know a mechanic or two willing to take off work to testify for you as to their experience with rapid oil loss and the subsequent damages experienced, rehearse a few questions with them to be sure they won't screw up too badly and tell them you can only reimburse travel expenses and a promise to owe them a solid should the need arise. Or, perhaps, if they were VERY GOOD and had courtroom experience, you could pay them a Day Rate as an Expert Witness which fees you could estimate and add to your demand for payment - worth a shot.
In Florida, I had a repair shop refuse to release my car without I pay him in cash money - no checks or credit card would be accepted (though he advertised acceptance of credit cards. I was able to bond my car out by paying the cash to the court conditioned upon a hearing to be scheduled. With an order from the local court in hand I was able to get my car back that day. The hearing was scheduled, he did not respond. My money was returned to me he got $0.00. In a sense, he admitted responsibility. You may be able to pull this off in your location - check it out.
If you do go to SCC, remember, only you can put your foot in your mouth. So plan what you are going to say (essentially repeat your written claim six ways from Sunday) and say as little else as possible. When questioned about facts of the case
PAUSE, if necessary or convenient, repeat the question to gather your wits so as to answer truthfully with minimal elaboration:
The Facts, Just the Facts. As you are NOT an 'expert' witness, you may confine yourself to answering only those FACTS you are privy to and answering
"I don't know," when the question might lead another to speculation or conjecture based upon "common sense" which might get you that taste of toe you wanted to avoid.
If you have the time, stop by your local community college and take Business Law I & II - couldn't hurt.