The short answer
Based on available data, the BMW M5 comes out ahead of the Cadillac CTS on fuel economy and power. Check the specs table and owner sentiment below for the full comparison before deciding between the two. Both are covered by real owner reports on CarWizz.
Overall
Sentiment is sharply divided by generation and is heavily influenced by ownership costs. The E60 generation (V10 S85 engine) is universally described as an unreliable "money pit" and "heap of junk" with catastrophic engine failure risks, particularly concerning rod bearings, leading to extremely high maintenance costs. The F90 generation (V8 S63 engine) receives a more positive reception for its brutal performance, all-wheel drive capability, and modern luxury, but is still acknowledged as a very expensive vehicle to maintain properly.
Best version to buy
F90 Competition (pre-hybrid V8): This generation is frequently cited as the "last good M5," praised for its reliability relative to the V10, monstrous performance from its twin-turbo V8, and attractive design. It is seen as a peak of the traditional M5 formula before the added weight and complexity of the hybrid G90.
Known issues
Overall
Sentiment is mixed and heavily dependent on generation and specific powertrain. The third-generation CTS (2014-2019) and its high-performance variants (CTS-V, V-Sport) receive significant praise for their handling dynamics, competitive performance, and value proposition when compared to German rivals. The Alpha platform is frequently cited as providing world-class handling, with some owners stating these models handled better than direct competitors.
Best version to buy
Insufficient owner data available to declare a single "best" version. High-performance V-Sport and CTS-V models are highlighted for their engaging driving experience and competitive performance.
Known issues
The verdict
The BMW M5 is the better choice for most buyers.
It has better fuel economy on its best-equipped version than the Cadillac CTS, based on the data above. If power matters more to you than running costs, the Cadillac CTS is worth a closer look instead.
Other comparisons
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Which is more reliable, the BMW M5 or the Cadillac CTS?
Owner reports show similar reliability sentiment for the BMW M5 and the Cadillac CTS. Check the known issues listed above for specific differences between the two.
Which is better for families, the BMW M5 or the Cadillac CTS?
Both seat a similar number of passengers based on our data. The BMW M5 is classed as a Station wagon, the Cadillac CTS as a Sedan, which affects cargo space and ride height for family use.
Which has better fuel economy, the BMW M5 or the Cadillac CTS?
The BMW M5 is more fuel-efficient on paper: 2.0 L/100km combined versus 13.8 L/100km for the Cadillac CTS, based on the best-equipped catalogued version of each.
Which is cheaper to maintain, the BMW M5 or the Cadillac CTS?
Exact maintenance costs aren't in our data, but owner reports mention cost-related concerns more often for the Cadillac CTS than the BMW M5. See the known issues comparison above.