Just wanted to share this story. I recently bought a 2005 Pontiac Grand Prix. The Carfax didn't show any service to the transmission so I was anxious to get that done. The car is fine but coming off the line from a full stop, the transmission would delay for a little bit and then snap into gear. I shopped around but most quick lube type places don't drop the pan and change the filter, they just want to do fluid exchanges. Speedee was the only place that would do it unless I went to a transmission shop. So I went to Speedee. I told the manager I wanted to drop the pan and change the filter and refill with Dexron 6. He gave me the option of Havoline Dex 6 (full synthetic) or their other Dex 6. Since the "regular" Dex 6 was $50 cheaper, I went with that. I saw while they dropped the pan and changed the filter, but when it came time to refill the transmission, the manager got their Chevron Dex III/Mercon ATF. I went up to him and told him I wanted Dex6. He said,"Oh this is a converted Dex6." I was confused, but I let him continue. He then mixed T3™ TOTAL TRANS TREATMENT™ with the Chevron Dex III/Mercon ATF. Got my car and drove away, but still confused and not quite convinced about what happened. Over the weekend, I drove the car and everything seemed fine. The shifting was improving, but I was not comfortable with the Dex III Heartland T3 mix. I searched the internet for Heartland T3 application sheet ( qmi-heartland application sheet ). It doesn't mention converting Dex III to Dex 6. Besides, I wanted real Dex 6, not additives. On Monday, I contacted Heartland and asked if Dex III with Heartland T3 was OK for a 2005 Pontiac Grand Prix. Heartland called and said that they do not endorse that for my car and that SpeeDee should not be doing that. They recommended QMI Multi-Vehicle Synthetic ATF – 6002. I then called Speedee and told them that Heartland does not endorse their practice of mixing Dexron III with T3 for my car. They told me that they would changed it out for Havoline Dex 6 but I would have to pay for the fluid price difference. No big deal, so now I have Dex 6 in my car. Speedee does this as a standard practice. Just putting it out there in case anyone has a similar experience.