# Gretio — user reviews > 18 indexed App Store user reviews of Gretio by Surreal Development LLC, rated 3.91/5 from 22 ratings. - Source: https://appshunter.io/ios/app/gretio/id1498320180/reviews - App overview in markdown: https://appshunter.io/ios/app/gretio/id1498320180.md - Rating breakdown: 5★ 15 · 4★ 1 · 3★ 0 · 2★ 1 · 1★ 5 ## Newest reviews (2 of 18) ### 5/5 — Duramax def test *2022-03-20* Used it to run a service bay test to check what was going on with my sensors and def system. App is awsome and I don’t mind paying the $20 so the devs can keep this app updated. Awsome job on this. Will be testing more with this app in the future. ### 5/5 — Must have app for 2018 Colorado ZR2 2.8 Duramax *2021-11-28, version 1.03* I got the dreaded exhaust fluid quality poor and I was 60 km away from being restricted to 8kmh. My scanner would not do anything and the dealer couldn’t get me an appointment for 3 days. I need to get around and go to work so I ordered an OBDLink MX+ on same day delivery. When it showed up I plugged it in and installed Gretio on my iPhone. Did a manual regen and then did a reductant fluid quality test. The test passed and the ECM was cleared. Total time to setup and fix the problem was about 30 minutes. I was very impressed with the app it is very plain and simple but packed with everything imaginable for my 2.8 Duramax Diesel. Also with bi directional communication it does more than any other app I have ever used. A lot of work must have gone into the programming of this app. Well worth the money spent. ## Most critical reviews (10 lowest-rated) ### 1/5 — Connectivity *2024-07-10* Could you please fix the issue of not connecting to the OBD Bluetooth device. It shouldn’t take 10 minutes and 87 attempts ### 1/5 — Gretio app *2023-10-06* Don’t waste your money on this one Very basic do nothing app that advertises as equal to torque 1 ### 1/5 — Does not support ‘old’ vehicles *2022-10-27* I was excited to purchase this app and happily pay for quality. I was highly dissatisfied given the description in the App Store did not give caveat that there is not a very long list of supported GM vehicles. I had to find out after sending an email to the developer. Once I got that email I had to go to the Gretio support site and find a link of supported vehicles. This link should be front and center in the app description so an informed decision can be made before purchase. ### 1/5 — Worked for Def/NOX but not injector calibration *2022-07-09* When CHanging injectors on a LML duramax you have to enter the code from the new injector both in the ecm and in the GPCM. This only seems to let you do the ecm, so you get an incompatibility code on your truck!!! Fix this please!!!! ### 3/5 — Connection problems with obdlink mx+ *2025-07-11* I bought the lml rpo pack and have been using gretio with the obdlink mx+ to monitor my 2016 lml duramax while driving. There are connection problems. I connect the obdlink mx+ to my iphone 11 pro running iOS 18.5, but when i then try to connect gretio, it doesn’t connect and the obdlink also disconnects and then has problems reconnecting. Ultimately , after factory resetting the obdlink and reconnecting from scratch, gretio will connect. But not always. Sometimes gretio still won’t connect and still disconnects the obdlink. Very frustrating. Sometimes it works and sometimes not. Something is not right. ### 4/5 — GM ultimate app! *2024-10-20* Many options and deep diagnostics on every module for these newer models! Great addition for a technician or at home mod fanatic! ### 5/5 — Phenomenal for 16 LML Duramax *2025-10-08* I bought the lml rpo pack and have been using gretio with the obdlink mx+ to work on my 2016 Chevrolet Duramax LML and it’s been great. From the egr cooler bypass valve to the reductsnt tank heaters to the NOX2 sensor, this has proven to be invaluable and helped save me thousands of dollars doing things myself. Highly recommended! ### 5/5 — Extremely powerful for the cost *2025-06-01* Worth every penny considering a dedicated scan tool with the same capabilities would cost you over a thousand bucks. I downloaded this app just for the service bay test function to clear the dreaded “poor DEF quality” countdown to limp mode on my diesel Colorado. Highly recommend! ### 5/5 — Incredibly Capable *2024-12-20* Though not super slick and sometimes crashes, this app is an absolute powerhouse for dealing with complex, intermittent sensor issues in modern diesels. Without question, I would not have been able to resolve my issue without it. Be sure to track down their troubleshooting guide if you are chasing diesel emissions issues. The guide brings context to the data and maps a path to resolution. **Developer response:** Thanks for the feedback, and I am glad it fixed your issues :) ### 5/5 — 2017 GMC Canyon with 19 miles before limp *2024-11-13* Found a forum where the author said he had a truck like ours with similar issues, and that he had an app for that! Bought the OBD link mentioned for $138 on Amazon and paid the $20 for the app. We also replaced the Nox sensor 1 to start fresh(er). Hooked the OBDlink up to Bluetooth, used the Gretio app to run the DPF Service Regen, (so cool to watch the soot percentage come down)then the DPF Reset, then the Reductant System Malfunction Warning Service Bay Test and all is right in the world again. ## Most praised reviews (6 highest-rated) ### 5/5 — Best $20 I’ve ever spent! *2024-10-23* Look, I’m a Soldier stationed overseas in Italy, NO GMC dealerships here. I got the dreaded “Exhaust Fluid Quality Poor” message in my 2017 Canyon, and I was freaking out, because I still have 3 years left in Italy. I swapped both NOx sensors and the speed limit warning did not go away, I kept searching and I came across the OBDLink MX+ and the Gretio App, I ran the Reductant System Malfunction Warning Service Bay Test through the Gretio App and BOOM! Problem solved! I’ll keep paying the yearly subscription out of gratitude for this fantastic app! Thank you! ### 5/5 — GM Diesel Enthusiast Must Have *2024-07-14* The combination of this app and its concise diesel emission trouble shooting guide are invaluable! Using them, along with OBDlink MX+, I was able to resolve the “Exhaust Fluid Quailty Poor” issue that was on the verge of bricking my LWN diesel. Being able to conduct diagnostic tests to resolve diesel emission issues removes the haunting fear of diesel ownership. I give thanks to the developer for sharing his skill and automotive passion! ### 5/5 — Cleared the dreaded DEF loop *2024-05-11* When all other scanners and code readers failed, this app let me do a service bay test that cleared that code after I changed my NoX sensors. Cannot say enough good things! ### 5/5 — Excellent *2024-04-27, version 1.06.09* Used it to force a regen and run a service bay test after replacing a Nox sensor. Ran both successfully. ### 5/5 — Advanced users *2023-10-14* This is an excellent app and a must have in my case. 2018 Chevy Cruze Diesel Needed to perform regens manually! I’ve initiated & verified a few, while cruising at speed. 👍🏻 Not many options for advanced GM OBD via iOS! Gretio fills endless gaps that I’m continuing to learn. Do your research before you dive in. Other users leave crappy reviews because they expect iOS like fuzzy interfaces. Manufacturers don’t make it easy to tap into their electronics- find a forum & discuss your vehicle and plans- The OBD MX hardware isn’t cheap either, so know the soup before you taste it. The developer of this program is very helpful! He’s quite active on various Chevy cruise forums I can verify! You want this if you expect such an important app not to break. ### 5/5 — Best app ever *2023-07-09, version 1.06.09* Don’t bother with the rest. Just get this app and you will have some control over your diesel. My truck Colorado 2.8 Diesel flashed power reduced DPF pressure to high. I was able to run (with this app) a regen of the DPF and the code cleared. If it wasn’t for this app I would have been a hostage of the dealer. Great app. Thanks --- *Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-15.*