Should the Touareg use 98 or 95 octane gasoline?
2 Answers
Touareg should use 95 octane gasoline, as this fuel grade is recommended in the vehicle's official owner's manual. In addition to checking the appropriate gasoline grade in the owner's manual, you can also find it on the fuel tank cap, which will be clearly marked. Generally, the fuel grade can also be determined based on the engine's compression ratio. Vehicles with an engine compression ratio between 8.6-9.9 should use 92 octane gasoline, while those with a compression ratio between 10.0-11.5 should use 95 octane gasoline. If the compression ratio is higher, 98 octane gasoline is recommended. However, with the application of new technologies, the fuel grade cannot be solely determined by the compression ratio. High compression ratio engines can also be tuned to use lower octane gasoline because factors other than compression ratio, such as ignition timing, turbocharging technology, and Atkinson cycle technology, also play a role. Generally, the higher the gasoline grade, the higher the octane number and the better the anti-knock performance. 92 octane gasoline contains 92% isooctane and 8% n-heptane, while 95 octane gasoline contains 95% isooctane and 5% n-heptane. If the Touareg occasionally uses the wrong gasoline grade, simply switch back to the correct grade after the current tank is used up. However, long-term use of the wrong gasoline grade can have the following effects: For vehicles designed for lower octane gasoline, using a higher octane grade will not cause damage, but the increase in octane number may alter the fuel's ignition point, leading to delayed combustion in the engine. This reduces the engine's power output and thermal efficiency, resulting in poorer performance. For vehicles designed for higher octane gasoline, using a lower octane grade can cause engine knocking. The significantly lower octane number reduces the fuel's ignition point, causing premature ignition during the compression stroke. If combustion occurs before the spark plug fires, resistance is created during the upward stroke. This resistance makes the engine run very unstably. Mild knocking may only increase noise without obvious engine damage, but severe knocking indicates serious engine conditions. The vibrations not only affect driving stability but also cause abnormal wear on pistons and cylinders, potentially leading to cylinder scoring in severe cases.
As a long-term Touareg owner, since purchasing it a few years ago, the manual clearly states to prioritize using 98-octane gasoline. The Touareg's engine is designed with a high compression ratio or turbocharging, and 98-octane fuel's higher octane rating effectively prevents knocking, ensuring smoother and more stable engine operation. After switching to 98-octane, I noticed quicker acceleration response, reduced noise, and effortless uphill performance on highways. Occasionally trying 95-octane, the power delivery felt sluggish, engine noise increased, raising concerns about potential long-term cylinder damage. Despite 95-octane being cheaper, for the car's health and to avoid costly repairs, I insist on 98-octane. With the car aging, extra caution is essential—repair costs are steep, and skimping on small savings could lead to major losses. I always check the manual reminder before refueling.
