I consider this a very serious ingestion. That chain saw oil can cause severe gastritis and really create serious damage to the esohagus, stomach and intestinal lining. That is in addition to any toxic effect impacting the liver or kidneys.
He has already vomited several times, and may be predipsosed to also developing pancreatitis from this ingestion.
So, I strongly feel that this is worth getting in to an emergency vet. They can offer very good antacids, anti-vomiting medication, and may still recommend giving activated charcoal suspension to bind up anything remaining in the digestive tract.
I think for me to just suggest giving an over-the-counter antacid would be a bad idea.
Wish I could do more.
To help settle the stomach you can use of the following, but not as a replacement for veterinary examination include
1.Pepcid A.C. (famotidine) comes in 10mg, 20mg, or 40mg tablets.
You can give it every 12 hours. You can give 0.5mg per pound of body weight. So, a 20 pound dog would get 10mg.
2.Prilosec (omeprazole). It comes in 10mg or 20mg tablets.
You can give in every 24 hours. You give 0.5mg per pound of body weight. So, a 20 pound dog would get 10mg
3.Zantac (Ranitidne). It comes in 75mg, 150mg, or 300mg sizes.
You can give it every 8 to 12 hours. You give 0.25 to 1mg per pound of body weight. So, a 20 pound dog would get roughly 1/3 tablet of the 75mg. Even with bigger pets, it is easiest to get the smallest size tablet. Even a 75 pound dog would only need one 75mg tablet.
4.Pepto-Bismol or Kaopectate
You can give it every 8 hours. The average dose is 1ml per pound of body weight, and that is the TOTAL dose for the day.So, if a pet weighs 30 pounds, they would get a total of 30ml a day or 10ml every 8 hours. This is dosing for regular strength Pepto-Bismol. If you use maximum strength liquid, give half as much.
Really consider an ER visit ASAP.
Hope that information helps. With proper supportive care, I would expect a good prognosis. Dr. Andy