Well, with a 35% market share in the installed market a lot of that is lube centers, and a lot of that is Jiffy Lube. However there are a lot if independent Jiffy Lubes (franchises) that do not feature Pennzoil. Can't really compare it to what Ford/GM/Chrysler is doing with rental companies as you do not rent oil, you sell it to the consumer, and market share is based off of consumer purchases.
Not sure what it's like in Indiana but in Wisconsin there are over 70 Pennzoil 10 Minute Oil Change Centers, each independent owned. There are only 3 or 4 Jiffy Lubes in Wisconsin and they are in Madison. They are part of a large franchise group and at one time they did feature Pennzoil but now their featured oil is Union 76, soley based on cost.
Anyway if you wanted to focus on a segment of the industry Pennzoil's largest volume sales are through the lube center business which includes independents, Jiffy Lube, and Wal-Mart.
If you look at market share on the retail side of the business, the top 4 would be the following:
1. Pennzoil
2. Castrol
3. Valvoline
4. Quaker State
The percentage points between these 4 is very little. Of course each brand has pockets of the country where they are number one, but overall these are the rankings.
A few examples close to me:
Wisconsin rankings: Pennzoil, Quaker State, Valvoline
Minnesota: Valvoline, Mobil, Pennzoil
Michigan: Western MI & the UP, Pennzoil, Quaker State, Valvoline. Eastern Michigan, Valvoline, Quaker State, Pennzoil.
I am originally from Texas and Pennzoil has a commanding market share lead in Texas. Next door in Louisiana, Castrol & Havoline are the market leader.
Now I'm retired and I rather talk about fishing